Here is the full list of all 24 FINAL FANTASY achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Earned all achievements.
Completed 100% of the Bestiary entries.
Defeated Chaos and restored peace to the world.
Collected treasure from 100% of the chests.
Obtained Excalibur.
Restored the Wind Crystal's light.
Traveled to all the map locations.
Restored the Water Crystal's light.
Gained titles of courage from Bahamut.
Collected treasure from 50% of the chests.
Completed 50% of the Bestiary entries.
Restored the Fire Crystal's light.
Reached level 50 for all party members.
Restored the Earth Crystal's light.
Collected treasure from 10% of the chests.
Obtained 100,000 gil.
Defeated 500 monsters.
Obtained 50,000 gil.
Defeated 300 monsters.
Played the 15 Puzzle game.
Obtained 10,000 gil.
Saved Princess Sarah by defeating Garland.
Completed 10% of the Bestiary entries.
Defeated 100 monsters.