Being dead has some interesting effects like being unable to punch or sprint, and collision is very wonky. It enables a decently-sized zip in Bonehell. Probably useful somewhere else too, haven't bothered to check. At any time during being 'dead' you can press start to instantly revert to a checkpoint. All you need to do to start a level dead is hold ESC on the main menu until you die, then hit continue.

To instakill house, just press ctrl, that's all.

(sorry for the late response, never got the notif)

That's super interesting! if there were some way to activate it mid-run that could be crazy useful (maybe F1 resetting to main menu after Benbo City?). I could see a zip like that making the Underground way quicker too. I'll play around with it and see what I can find.

Does the ctrl instakill only work on the house?

EDIT: I was rewatching a stream I did a couple days ago and found something similar. After the bike section in Benbo City, i was pushed into the loading zone during the dismounting cutscene. I entered sideways and started the Barrier fight the same way. Looks like I was technically able to punch but the game crashed when I tried.