Zora Mask BA deserves a page by itself due to it being the most flexible tool concerning getting items on B.
Zora Mask on C-right is linked to your Swords & Shields. Here's the values of these items within the byte:
|Zora Mask on C-right|
|what item||binary value||decimal value|
|Biggoron Sword / Giant's Knife||00000100||4|
|Flag: is the Giant's Knife broken||00001000||8|
The Giant's Knife and Biggoron Sword actually have the same value here. The difference between the two is stored elsewhere.
As you can see the trigger if the Giant's Knife is broken or not is stored here as well. Using Zora Mask RBA, you can get this flag active without having the Giant's Knife. This will place the symbol of the Giant's Knife into your inventory, but you will be unable to select it or use it.
Collecting Biggoron Sword changes this a little bit. If both broken and sword variables are active then nothing of interest happens but if only broken is on then the icon shown is a full sword.
The reason the Zora Mask is the most flexible tool for Bottle Adventure is because of the wide range of possible values. Every bit is used except for the last one (128). This gives a range of 0-127, which covers every normal item and a large number of the glitched ones. For more info on this, view the Item Chart.
When it comes to placing items onto your B button, the item on Child Link's C-Right is the one checked by the game. If it was Adult Link's, you would be able to use items such as the Poacher's Saw or the Broken Goron's Sword on C-Right to get the full range of values (0-255). This isn't possible, and Zora Mask is the closest we can get with Child Link. This isn't a big loss considering items 128-254 are all glitched, and 255 is Blank button.
Due to the difficulty of setting up exactly which swords & shields you need to have, I would recommend using Poe on C-Right (links to Bombchu count) if you ever need to place items 1-50 onto your B button. Zora Mask is useful for when you need items 51-127.
If you need item 0, Steal the Rod and you get Deku Stick on B.