Mars Story:
To play mars story from the start, don't let Sephy or Zeus join your group when asked. Mars story will become available.

Restart battle a losing battle:
If you are losing a battle, pause the game and change weapons (select "Equip"). Now resume the game and you will find yourself at the begining of the fight, with full health.

Get Mar:
To get Mar to join your party at the start of the game, talk to everyone on deck, but do not let them join your team. Walk back to the cabin just before you enter Magnus and Cleo run up, say a few lines, and then the dragon will attack. After the fight Cleo will wake you up. You will hear a flute playing. Player mode will switch to Cleo and you will go up the cliff, past the waterfall, and on to Mar.

Full Health:
Pause the game if you are losing a battle. Then hit ''equip'' and resume the game. You will be at the start of the battle, with full energy.

Defeating Gaia:
Equip the Hand of Pyro and Bite of Lightning. Attack and destroy the two arms, then the white-orb. Block all the attacks Gaia does. Use Bite of Lightning to easily destroy the little robots Gaia throws at you. Do not call the Elemental Summon; you will not have enough time. When only the head remains, shoot Hand of Pyros at Gaia until he dies. Remember to block all attacks.