I managed to find a way to record myself and, while attempting the speedrun, not only did I find the glitch, but I found a second one that could be very useful for the 100% category :

the fall glitch can be found is at 1:11. I don't know what triggers it the other glitch is at 0:09 : basically, I get punched by a guy, but when the level ends, I still get the checkmark for completing the mission "do not get punched" ("ne te fait pas frapper" in french). I think it's because, since I reacted fast enough with kimmy's katana, it cancels the punch

hope these discoveries will help revive this community.

since I don't speedrun myself I don't have any capture of the glitch, and I do have trouble remaking it. however, I think I found a glitch.

as you know, falling for more than two stories of a building counts as an instant death. however, I managed a few times to cancel the kill plane by getting through a window.

this is already know, however, I did manage to do it AFTER falling for more than two stories. I think this has to do with movement (aka, already having speed to go towards a window before hitting the kill plane) and hitting the window before the characters animation change to the instant death.

usually, when I managed to do it, It usually went like this : Fell through the window going right, going left when at the same height as the second window, and, as the death scream begins, hitting the window 3 stories down from the start.

I hope this will be useful to speedrunners. good luck!