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