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.
Welp, there you go.
Screw around in the fireplace.
Stop looking at the damn picture.
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.
A sizeable achievement.
Find the developer's future game concept art.
Complete the last level with a single bullet.