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 the Tome artifact.
Find the Skull artifact.
Break the code.
Find the Writing Cube artifact.
Find the Counting Cube artifact.
Find your very first cube shard.
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Find an Anti-Cube.
Find ALL collectibles.
Get to the end.
Collect all 32 Golden Cubes and 32 Anti-Cubes.
Reactivate all 5 warp gates.