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.
Find the Tome artifact.
Get to the end.
Find the Counting Cube artifact.
Break the code.
Find the Writing Cube artifact.
Find your very first cube shard.
Find an Anti-Cube.
RTRTLTRTRTLTLTLT