Using the Reverse BiTMagic technique combined with Minecart Escort Skip and the Early Gorge BiTWarp, it is possible to trigger a Fi textbox that will completely heal the Thunder Dragon before meeting Levias. This allows access to the Boss Rush early, which can be used for many sequence breaks.
Once that is done, perform BiT and set the flag that triggers the Fi Text that is for saving the Thunder Dragon (2x20). There are two ways to set this flag, both require going to Faron in Back in Time.
Once that flag is set, the Fi text will trigger. This will heal the Thunder Dragon, as you can now hit the timeshift stone and you will be able to do the boss rush, even if you did not meet Levias. This does not give you the song of the hero part in your inventory, but you will still be able to heal the Thunder Dragon for real later to learn the Thunder Dragon's Song, and you will still be able to learn the Song of the Hero from Levias. You will also be able to use the Groosenator to Lanayru once the 2 other dragon quests have been completed.
In the Sealed Grounds, the flag corresponds to playing the harp tutorial with Impa. To perform this RBM, you must have obtained the harp.
Activate BiT, and go to Faron in BiT. Watch the Groose cutscene at Behind the Temple, and enter the Sealed Temple without reselecting any file. Inside the Sealed Temple, wait for the cutscene with Groose and Impa to start before opening the Splash Screen. You must now play the harp tutorial with Impa. Start your file before ending your last strum to RBM scene flag 2x20 into the Lanayru Gorge area.
Note: You do not need the B-Wheel to perform this RBM despite needing to play the harp.
In Faron Woods, the flag corresponds to opening the Doors to Skyview Temple. This requires going to Deep Woods in Back in Time, and hitting the crystal to open the Skyview Temple doors. This can be done with the slingshot, or by using BiTMagic to set scene flag 2x10, which will hit the crystal remotely.
Start your file right as Link walks out of the camera view during the crystal hit cutscene to RBM scene flag 2x20 into the Lanayru Gorge area.
All of the boss fights in boss rush take place on the same maps as the regular fights. To make this work, the game will deactivate certain story flags which it assumes you must have already activated if you've made it far enough to access boss rush normally. After the fights are over these flags will be set, even if you did not have them before.This is the case with several bosses.
Fighting the Imprisoned 1 gives the following story flags early:
This is because if these flags were set, the Imprisoned 1 fight would act abnormally (no racetracks or strange Groose behaviour). The Farore's Courage obtained flag can be used to get the Water Dragon's Scale without going to the Isle of Songs to learn Farore's Courage, because it sets the Faron Woods layer that can make the trial gate appear. The Imprisoned 1 defeated flag allows skipping that fight in 100% speedruns (see Early Thunderhead and Scrapper).
Fighting the Imprisoned 2 gives the story flag for having defeated the Imprisoned 2 early. Combined with the previous rematch (since the Imprisoned 2 fight crashes if you've not completed the Ancient Cistern for the racetracks to appear), this gives all the story flags needed to be able to open the Gate of Time, and can be used to beat the game while skipping the Ancient Cistern, Fire Sanctuary, and the Imprisoned 2 fight.
Fighting the Horde sets the Horde Cutscene as watched, but that flag will always unset upon finishing the rematch, so you cannot keep it (unless a way to save at the statue during the Horde to escape is found). However it also gives the scene flag that unlocks the door from Hylia's Realm back to Hylia's Temple (7x08), which you can keep. You can use this to reload the area in the Ghirahim 3 rematch by doing the escape trick and then going in and out of the Temple. However, this is not useful because doing this requires having access to Hylia's temple layer 1 or 2 (for the door back to Hylia's Realm to exist), which requires having already opened the Gate of Time or beaten Sky Keep, and having scene flag 7x04 in the Sealed Grounds to open that door, which is normally set after beating Sky Keep.
It is possible to escape the Ghirahim 3 fight in the boss rush minigame by accessing the bird statue at the bottom of the arena which is normally blocked off. By saving and reloading at this statue, the minigame flag goes away and the game instead puts you into the real Ghirahim 3 fight. To properly continue the fight, you then have to get out of the walls that normally block the statue and then void out to respawn on the platform that Ghirahim 3 is standing on. This can be used to skip opening the Gate of Time, Sky Keep and the Horde fight.
Go to the Thunder Dragon and choose to fight Ghirahim 3 (note that you can only do this without first fighting Ghirahim 3 if you're playing on Hero Mode). At the beginning of the fight, walk around Ghirahim about 180 degrees so that you line him up in the proper direction and hit him off of the platform. Hang off the ledge of the platform above Ghirahim in order to stop the platform beneath you from moving, and wait for Ghirahim to get back up and for the lower platform to grow in size. Once this happens, wait 4 more seconds, and then drop down, turn around, and begin hitting Ghirahim again. The platform you're on will begin to move horizontally and ideally, you'll knock Ghirahim off of the edge right before the platform begins to move vertically again. This will cause Ghirahim to fall onto a lower platform from before, and from here you'll want to repeat the process starting from hanging on the ledge again. If you knock Ghirahim off too quickly, then he'll be further away from the higher platform, and after dropping down to the platform on further cycles, the platform may move upwards immediately instead of only moving horizontally at first. On further cycles you also want to make sure that you jumpslash after letting go of the ledge so that you can turn around as quickly as possible to begin hitting Ghirahim again. After doing this for at least 4 cycles, the platform Ghirahim lands on should be low enough that you can jump into the area where the bird statue is, and save to reload to the real Ghirahim 3 fight.
Unfortunately, after saving at the statue, you are surrounded by walls and you cannot escape normally. To escape from the statue area and beat the real Ghirahim 3 fight, you must perform one of the following methods.
By going into first person and walking backwards into the acute corner near the bird statue, you can make Link slide at an angle that continuously pushes him upwards between the two walls of the acute corners. If your angle is correct, Link will jump into the main battle arena where he normally fights Ghirahim during the 2nd and 3rd phases. From here it's possible to clip out of the arena to the main spiral area as seen in the video below : you can get the angle needed for clipping through the fence by using some camera properties in the spiral. You need an angle between -7160 and -7300 to clip with a front hop, and the method below gives you a consistent angle of -7184. You can then run up the spiral to trigger the void out that will bring Ghirahim and his platform back down to Link. You want to void out as far away from the center of the spiral as possible so that Ghirahim's platform is away from the spiral fence that resides on the inside of the spiral. This will allow you to then hit Ghirahim over the fence and perform a final blow over the fence to continue the fight as normal since the platform will fix itself.
You can escape the statue area using Back in Time. To do so, activate BiT and go to Faron in BiT. Perform a BiTWarp at the Sealed Grounds Spiral Statue. You can now jump down to be at the same height as Ghirahim 3. Wait for Ghirahim 3 to walk in the air over to you. Once he has reach the walls, perform 2 down to up spin attacks to knock him down. Run up the spiral a little and perform an ending blow to get over to his platform. You can now defeat Ghirahim 3 normally, and the Ghirahim 3 Escape is completed. This method is slower than the one above.
The Fi text also sets the Volcano Eruption in Bokoblin Base to be ready, meaning that this gives you access to the Bokoblin Base early, before even having the fireshield earrings. Trying to enter the Bokoblin Base this way will cause it to be in layer 0, meaning the items won't be there. You can hovewer force a layer 1 load by talking to the sheikah stone and going into the hint screen. This allows you to obtain items early, and also access the Fire Sanctuary without the fireshield earrings. This is used in 100% speedruns for that matter.
To do this, you must use Faron BiT to enter Bokoblin Base while still keeping all of your items. For this, follow the steps:
Because your run file was saved at a statue, you will be able to enter Bokoblin Base while not triggering the Eruption Cutscene, which is responsible for the loss of your items and for being locked in the jail cell. On layer 0, being locked inside the jail cell gives you no way to escape. Reload by going into the hint screen of the Shiekah Stone. After cancelling you will be in layer 1 and you will be able to get all the items.
Note that obtaining the Fire Dragon's Song before meeting Levias locks you out of being able to talk to Levias for the first time to properly start the SotH quests. More importantly, this means Flooded Faron Woods will always be on layer 0, making it impossible to complete. More generally, that also makes starting SotH quests impossible outside of more BiTs. Thus, it is preferable to wait until meeting Levias before completing Bokoblin Base if you need to do more of the Song of the Hero quest. Note that this only happens with the Eldin Song of the Hero quest, if completing the Faron SotH or Lanayru SotH quests early were possible it would not cause this issue. This happens because when talking to Levias, the Eldin Song of the Hero quest is checked first for Levias' dialogue.
Using Bokoblin Base, you can obtain early items, and especially clawshots early. You cannot obtain the bow, the bug net or the beetle however, as they are in a special chest that acts differently from the others (that chest does not give you items, it unrestricts their use). Thus, to obtain the bow after Early Bokoblin Base, you must enter Sand Sea, and that requires obtaining a small key to use in the Lanayru Caves. Unfortunately, the Minecart Escort Skip sets Lanayru Gorge to layer 2, making the Gorge key unobtainable, and the Fi text sets Lanayru Caves to layer 2, making the Cave key also unobtainable. If you wish to go to the Sand Sea after performing Early Bokoblin Base, you should setup Early Boss Rush on a different file, and Reverse BiTWarp a file that has done Minecart Escort Skip but not triggered the Fi text for Early Boss Rush yet into Bokoblin Base. Entering the Bokoblin Base without watching the Volcano Eruption causes every chest in Bokoblin Base to have their normal "GetItem" event. This means opening the clawshot chest afterwards will also give you the story flag for having beaten the Lanayru Trial, thus setting the Lanayru Caves to layer 1, making the Cave key obtainable. You also simply need to go back to Gorge to set Early Boss Rush on that file if you wish to later.
Because you have items in Bokoblin Base with this trick, you can use the timesavers documented here.
Thanks to the Reverse BiTMagic technique, it is possible to set the statue right next to the Fire Sanctuary entrance to have been checked. This allows you to fly to it and skip pouring water on the frogs. Combined with Water Basin Skip, this allows for completely skipping the Adventure Pouch and the Bottle, and combined with Early Boss Rush and Early Bokoblin Base, it allows access to the Fire Sanctuary and the Volcano Summit without the Fireshield Earrings, because the Volcano Summit and Bokoblin Base share the same scene flag space, making this a pretty sizable skip.
The corresponding flag is Dx20. In Lake Floria it is set by the Entering Ancient Cistern Cutscene. This requires a file that has completed Farore's Silent Realm but not entered/beaten the Ancient Cistern yet.
The fireshield earrings are normally required to remove the fi trigger in front of the Volcano Summit, which makes it impossible to enter. However, this fi trigger only exists on the normal Eldin stage, and not on the Bokoblin Base stage. There are two versions of the Volcano Summit: one for Eldin Volcano, and one for Bokoblin Base. However, there is only one stage for the Fire Dragon's Room, and that stage can be accessed from both versions of Volcano Summit. Leaving the Fire Dragon's Room will load the Bokoblin Base version if you've not beaten Bokoblin Base yet, and the normal version if you did beat Bokoblin Base. Using this fact, it is possible to enter the normal Volcano Summit without the fireshield earrings.
First, perform Early Boss Rush and then Early Bokoblin Base. Enter the Volcano Summit (Bokoblin Base version), and save and quit at the statue. Copy your file over to slot 3. Then on file 3, enter the Fire Dragon's Room and get the fire dragon's song. Once Bokoblin Base is beaten on file 3, save and activate BiT. Perform a bed or death trick by starting your file still saved in Volcano Summit and open the splash screen during the fadeout to perform a file dupe teleportation. This will allow you to load back to the Volcano Summit (Bokoblin Base version) with a file that has beaten Bokoblin Base. Enter the Fire Dragon's Room again and leave immediately. Because you've beaten Bokoblin Base, you will now load into the normal Volcano Summit map. This skips the fireshield earrings.
Due to the Volcano Summit area being an heated area, a Guardian Potion + is highly recommended to get through this trick.
After performing Early Boss Rush, it is possible to enter the Koloktos fight in Boss Rush. Normally, the door flags during rematches are zone flags or temporary flags, which makes them impossible to use to our advantage. Koloktos however is an exception, as the flag for unlocking the door back into the dungeon is a scene flag. It is thus possible to set early with the Reverse BiTMagic technique.
The corresponding flag is Ax02. On BiT Skyloft it is set by obtaning the bottle in the Bazaar or by buying anything from the Item Seller. This requires a file that has either the pouch, the slingshot, bombs or the bow. To do this trick, enter the Ancient Cistern normally, save and activate BiT. Enter the Bazaar with the file that has one of the items listed previously. If you have the pouch, buy the wooden shield and start your file on the last textbox to perform the RBM. If you have another item, check the wooden shield to set room 0 zone flag 1x20, then buy what you can buy without reselecting your file (seeds with slingshot, bombs with bomb bag, arrows with bow). Perform the RBM by starting the file on the last textbox from the item seller. Commit the RBM then leave the Ancient Cistern and enter the Koloktos fight in Boss Rush. You can now use the door behind you to leave and escape Koloktos in Boss Rush.
After performing the Koloktos Escape above, save at the Boss Door Statue in Ancient Cistern. You cannot fight Koloktos yet, as this would warp you back to Lanayru Gorge. The ending door is also impossible to unlock in this state. To circumvent this problem, perform a bed or death trick to file dupe and teleport another file to the Ancient Cistern Boss Entrance. This file will not be in boss rush state, and can fight Koloktos normally. This skips the Boss Key.
On Normal Mode, Ghirahim 3 Escape cannot be used because you cannot fight Ghirahim 3 in boss rush until you've defeated it normally. Thus, beating the game requires going through Hylia's Temple and opening the door to Hylia's Realm to fight the Horde. The cutscene before the Horde fight cannot play correctly until you've beaten Sky Keep, and you cannot skip that cutscene on Normal Mode (you need to watch it at least once to be able to skip it). Thus, Normal Mode speedruns normally need to beat Sky Keep.
There is however a way to skip Sky Keep on Normal Mode using Koloktos Escape.To do so, you must perform the Koloktos Escape above. You must also open the Gate of Time and meet Levias (in order to reach Hylia's Temple in Back in Time), which requires the True Master Sword and the Spiral Charge. Once that is done, perform a Reverse BiTWarp into the Horde Cutscene. The steps are the same as explained here, under Reverse BiTWarp into Horde Variation, but instead, you must start your file as you are opening the door to Hylia's Realm. If you are saved at a statue, this will spawn you in Hylia's Realm with control of Link instead of playing the Horde cutscene. Now, because of escaping Koloktos, the boss rush flag is still active. This flag sets Hylia's Realm to layer 1, which allows us to fight the Horde, despite never watching the Horde cutscene (normally, a Reverse BiTWarp into the Horde Cutscene puts you in an empty Hylia's Realm). The walls around the spiral also don't exist due to the Reverse BiTWarp. Jump straight down and activate the last bokoblins by running into their trigger. Defeat all the bokoblins that spawn to set the Horde as defeated. Sadly, because of the boss rush flag, the load at the end of the fight does not happen, and Hylia's Realm is stuck on layer 1. Thus, you need to save the game at the statue and BiTSave back to Skyloft. Fly to Lanayru Gorge and die (or beat) any boss to unset the boss rush flag.
Once all of this is done, you can now go back to Hylia's Realm to skip Sky Keep. The best method to do so is to perform a Reverse BiTWarp into the Horde cutscene again. You are now back to Hylia's Realm without the boss rush flag but after beating the Horde, thus you have access to Hylia's Realm layer 7. Run into the cutscene trigger to start the Ghirahim 3 fight. This skips the Horde Cutscene problem and thus Sky Keep on Normal Mode.
This Reverse BiTMagic technique allows one to talk to Groose and start the Faron Song of the Hero Quest early thanks to the help of Early Boss Rush. By setting the correct scene flag with RBM in the Sealed Grounds, and then choosing to fight the Imprisoned 3 in Boss Rush, you can run towards the Groosenator, where there will be thanks to the RBM a cutscene trigger you can step into. This cutscene sets the Faron Song the Hero Quest as having started. The main use for this trick is for unsetting the story flag for the Eldin Volcano Eruption: thanks to this RBM, you can enter Eldin Volcano at will without going into Bokoblin Base, despite having performed Early Boss Rush.
The corresponding flag is Cx10. On Skyloft, it is set by the gratitude crystal in the pumpkin patch; in order to achieve this during BiT, RBM must be used to enable gratitude crystals on an early game file. Thus, while this RBM itself is quite fast, it unfortunately has a pretty long setup required. Because of Sealed Grounds layers, this does not actually allow you to do the Faron Song of the Hero quest before meeting Levias. The only useful thing it does is to disable the volcano eruption.
Note: If you intend on completing the Song of the Hero quest, this trick forces you to complete the Faron Song of the Hero quest first.
Performing Early Boss Rush and choosing to fight the Imprisoned 1 sets Ancient Cistern and Fire Sanctuary as defeated. This causes the boss doors in those dungeons to become unopenable the normal way. You must thus perform Boss Key Skips to beat these dungeons. See Ancient Cistern Boss Key Skip and Fire Sanctuary Boss Key Skip.