Zone 8
Defeat the Zone 7 Boss to complete the game and see the normal ending. Save the game when prompted and get the final orb. Reload your cleared saved game, then complete all seven training rooms. Zone 8 will now be unlocked at the world map. 

Alternate ending
Defeat the Zone 8 Boss. 

Hard mode
Collect all Medallion fragments and orbs, complete all seven training rooms, and defeat the Zone 7 and 8 Bosses.