Here is the full list of all 12 FEZ achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Find ALL collectibles.
Get to the end.
Find the Tome artifact.
Find the Skull artifact.
Find the Writing Cube artifact.
Reactivate all 5 warp gates.
Break the code.
Find your very first cube shard.
Find the Counting Cube artifact.
Find an Anti-Cube.
Collect all 32 Golden Cubes and 32 Anti-Cubes.
RTRTLTRTRTLTLTLT