Here is the full list of all 9 Vapor Trails Demo achievements.
Take the fast way across the lake.
Give Tara cigarettes immediately after she asks for them.
Unlock all extra attacks.
Reach the furthest point of the demo.
Prune your first lookahead branch.
That Beast Can Smoke
Defeat your first boss.
Start your first lookahead branch.
Get the pumpkin without unlocking the wallclimb.