Here is the full list of all 10 Only If achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
A sizeable achievement.
Solve Vinny's riddle on your first attempt.
Press E on every single bloody thing.
Complete the White Pawn Scenario.
Complete the Black Pawn Scenario.
Stop looking at the damn picture.
Screw around in the fireplace.
Welp, there you go.
Find the developer's future game concept art.
Complete the last level with a single bullet.