By using Angle Retention, we can push a pillar out of bounds, which disables the screen transition. By going out of bounds, we can enter a further room, skipping two minecart trips, hitting a lever, and using a small key. When out of bounds, the easiest method to reach a further room is to roll up four times, then right twice, then open and close the pause menu when you see a screen transition. Note: in most cases, you ill want to retrieve the small key from the chest after disabling the screen transition.
By using Angle Retention, it is possible to push a pillar into a wall, then damage boost off of a rollobit to clip out of bounds and walk straight to the boss room.
You can skip a cycle at the set of 5 moving lava platforms in the boss door room. By moving to the top right of the first platform, it's possible to walk across to the third platform without having to wait for another cycle. (Video when ready.)