Which route do I play first and which route do I play last to unlock the 18+ version?
Viewing post in Requiescence (BL Visual Novel) comments
You don't need a route to unlock 18 plus, you just download the 18+ game. There's multiple options, for PG Itchio game, PG steam game, 18+ itchio game, and 18+ steam game.
You need to check you downloaded the one you actually want first.
All routes have potential 18+ content, provided you downloaded the right one for that.