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.
Reached level 50 for all party members.
Collected treasure from 100% of the chests.
Defeated Chaos and restored peace to the world.
Obtained Excalibur.
Restored the Wind Crystal's light.
Traveled to all the map locations.
Restored the Water Crystal's light.
Restored the Fire Crystal's light.
Collected treasure from 50% of the chests.
Gained titles of courage from Bahamut.
Completed 50% of the Bestiary entries.
Restored the Earth Crystal's light.
Obtained 100,000 gil.
Obtained 50,000 gil.
Defeated 500 monsters.
Collected treasure from 10% of the chests.
Defeated 300 monsters.
Obtained 10,000 gil.
Defeated 100 monsters.
Played the 15 Puzzle game.
Completed 10% of the Bestiary entries.
Saved Princess Sarah by defeating Garland.