Those puzzles are pretty hard to guess for me. I know door 1 is referring to the catbox.moe link that opens after the bonus of this version, door 2 being some kind of link I can't really find, and door 3 just being "the key" even though I couldn't find the exact link it's referring to. The new version is just an ARG I couldn't solve. Maybe I should just turn back and forget it.
Update: I solved it.