How do you do all the quests in Kingdom Hearts recoded?

Answer 1

To complete a quest you must retreive an item for a character in that world (Selphie in the beach, Cid in traverse, etc.). To get these items, you much go into the system sectors, build up your CP, and redeem the CP for items at the end of the sector.

To do all of them, you will have to go back to each world through questploration to find new System sectors. Some may not be available until you pass certain requirements (beat Agrabah, beat the game, etc.) and may require a certain level of "Scan" be unlocked in the Stat Matrix. Once you beat the game and unlock Scan lvl 4 you should have access to all system sectors.

The only world that differs from this pattern is the Olympus Colliseum. To get 2 of Phil's items, you actually have to choose Replay Episode and go back through the colliseum floors. The first time you choose Replay, and talk to Phil, it will give you an option of 5 or 15 floors. You must choose 15 floors and beat the rock titan to get a quest item. After that, you choose replay again and choose the newly unlocked 30 floors, then beat the Ice Titan on floor 30 to get another quest item. The 3rd quest item is available through standard questploration in the only system sector for that world.