I've compiled a small list of tricks that can't be used yet but could have potential use if someone can do something with them.

Level 20 gap skip without using beast mode: This could possibly be used in impossible runs since farming beast mode takes forever on impossible.

Going out of bounds in level 2: Level 2 is connected to level 14 similarly to how level 5 is connected to 16. I couldn't actually do anything with this tho.

Going out of bounds in level 4: Couldn't find a way to go back in bounds.

Climbing the mountain in the first part of level 20: If you can skip the part where you're trapped by fire in the tunnel, you'd save a lot of time but i couldn't figure out a way.

Climbing the mountain in level 12: If executed perfectly this is actually a small time saver in the all levels run. You can get to the other side of the river with this too but you're a bit stuck behind trees and can't exit the level.

SolusOHKO found a way to go from lvl 2 to level 14, this alternate route seems slightly slower and A LOT harder tho. I'm going to leave a video of my run here. It's not a perfect run, it could be 50 seconds faster at the very least but it should at least show a good route using this strat.