Here is the full list of all 30 FINAL FANTASY IV achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Earned all achievements.
Exchanged the pink tail for Adamant Armor.
Found and learned all secret summon magic.
Completed 100% of the Bestiary entries.
Defeated Zeromus and restored peace to the world.
Collected treasure from 100% of the chests.
Obtained all sealed equipment.
Traveled to all the map locations.
Obtained all hidden items.
Learned all non-secret summon magic.
Defeated 500 monsters.
Defeated 1000 monsters.
Reached level 70 for all party members.
Defeated the four elemental lords again.
Obtained the Lunar Whale and landed on the moon.
Obtained Excalibur.
Defeated Rubicante, the Lord of Fire.
Completed 50% of the Bestiary entries.
Obtained 500,000 gil.
Collected treasure from 50% of the chests.
Arrived in the underworld.
Defeated Barbariccia, the Lord of Wind.
Defeated Cagnazzo, the Lord of Water.
Obtained 100,000 gil.
Climbed Mt. Ordeals and became a paladin.
Defeated 100 monsters.
Completed 10% of the Bestiary entries.
Obtained 10,000 gil.
Collected treasure from 10% of the chests.
Accidentally destroyed the village of Mist.