These new difficulty modes will be available on a new game file after completing the necessary tasks.
First off, you must witness the Private Action in Kurik where a woman named Philia is warning the citizens to evacuate the city. Next, you must reach the final save point in Phynal. After that, you must leave Phynal and view a Private Action in Centropolis. You'll find Philia again in the lobby of the main building. After you talk to her, Gabriel's limiter will be removed and he will be much more powerful than his original form. It is recommended that you go through the Maze of Tribulations and get your levels very high (120+ at the very least) before attempting to fight him.
There is a secret dungeon in the game called the "Maze of Tribulations". To unlock it, you must use the save point right before fighting Gabriel. Your save icon should turn blue. Then, return to the arena in Fun City, and talk to the old man in the stands in the north side of the arena. He says he can recover your memories; accept, and you'll return to Arlia on Expel. Leave Arlia and you'll have your Psynard; the Maze of Tribulations is located at the lone dot on the desert island, southwest on the world map.
Beat the game once on any difficulty, and you unlock the Voice Player.Beat the game with additional characters in your party to unlock their respective voices.