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.
Press E on every single bloody thing.
Complete the last level with a single bullet.
Solve Vinny's riddle on your first attempt.
A sizeable achievement.
Complete the White Pawn Scenario.
Find the developer's future game concept art.
Complete the Black Pawn Scenario.
Welp, there you go.
Screw around in the fireplace.
Stop looking at the damn picture.