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