Full list of all 18 Final Fantasy III achievements worth 200 gamerscore. It takes around 200-300 hours to unlock all of the achievements on Windows Phone.
Complete the entire Bestiary.
Defeat Iron Giant.
Defeat the Cloud of Darkness.
Open every treasure chest.
Obtain the Ultima Weapon from the Legendary Smith.
Attain level 99 with all jobs.
Obtain every weapon in Eureka, the Forbidden Land.
Save up 500,000 gil.
Defeat Titan and obtain the Earth Crystal.
Obtain all the summonable creatures.
Attain level 99 with any job.
Open 50% of all treasure chests.
Obtain a summonable creature.
Complete 50% of the Bestiary.
Defeat Kraken and obtain the Water Crystal.
Save up 50,000 gil.
Defeat Salamander and obtain the Fire Crystal.
Defeat Djinn and obtain the Wind Crystal.