By 5th level, you mean the one where the 2 characters are seperate and there's a conveyor belt?
If you fell off the belt, there's still an area with a teleporter where you can return to the belt, but you can still control the companion to activate a blue platform that leads to an area with 2 keys.
The game is pretty much my first, where I used it to learn stuff and also an excuse to show off characters and settings I thought of for a while.