Final Fantasy Crystal Chronicles: Echoes of Time Cheats
Replay Boss Battles
First you have to beat the boss once, then you can go back and find a warp point that will take you back to that boss so you can fight the battle again.
Ring of Fates Bosses
Get all the events in the Library, then go back and clear the enemies in the first area. This will unlock a warp point that takes you to where you can fight the bosses from Final Fantasy Crystal Chronicles: Ring of Fates. Place the book on the bookstand to fight.