Downgrade crash

So, me and my friend decided to downgrade the game version to 1.0, and check out stuff in KYF [ Kill Your Friends ]

But, when I downgraded the game, I opened it, it said "1.0" and I saw the old menu, etc...

Buut... there's only one problem !
When I click on KYF, my game crash :/

Does anyone know why it's crashing ?

This game crashes very often in 2.0 what do you expect from 1.0?

Don't know why, but any version earlier than 1.2.1 (around Oct 2016) may cause serious issues beyond not working, and you're advised against downgrading to those.

Anyone with more experience than me can elaborate. 1.2.1 is the Halloween chapter patch I believe.