If you jump and pause at the same frame you can do this repeatedly to gain infinite height. The timing can be a bit tricky, to make it easier you can :

1. If you have a controller it seems mashing Esc and jump while also mashing pause on the controller makes it a little more consistent. Also makes it easier to move around with the analog stick.

2. Another way to do it pretty consistently is by binding jump to F1 in addition to spacebar so it's closer to ESC.
   

Furthermore, the lower your fps, the easier it is.

Using that, you can get Oob. They are boundaries everywhere in the levels, but in between the levels there is no ceiling. I've been able to oob in every single level except for ice cave and the second tutorial/level because there is always a ceiling in those ones To get back in bounds to end the level, the fastest way I've found, is to trigger the last save/dialogue from outside the boundaries then to quit/continue to get in bounds

Shoutout to ClashCode for finding this glitch