Successfully complete the game with an 'S' rank on all missions.
Copy-x Mini-game
Successfully complete the game under the hard difficulty setting.
Defeating Inarabitta
The most effective way of defeating this Boss is to use Recoil Rod + Hyper jab (the Ex skill from Deathtantz Mantisk). Because your Hyper Jab destroys his missiles/torpedoes, all you have to do just charge straight up to him and press Jab repeatedly. He may sometimes leap away or fire the arrow beam. This does not matter because it is well worth it. If you have the Fire Armor, put it on and it will be an even swifter victory.
Ex Skill
Complete a Boss scene with an 'A' or 'S' rank to get an Ex Skill. There are twelve Ex Skills available.
Fefnir Mini-game
Complete all missions with 100 points.
Hard Difficulty Setting
Successfully complete the game, then highlight the 'New Game' option at the main menu, hold L and press Start.
Harpuia Mini-game
Use zet zaber from the opening to the end, and finish the game with an S rank.
Leviathan Mini-game
Complete all missions with 100 points.
Phantom Mini-game
Use buster shot from the opening to the end, and finish the game with an S rank.
Super Zero
Customize Zero like this...
Head: Auto charge chip
Body: Thunder (yellow) body chip
Feet: All feet chip
Now you should be able to dash through certain foes, double jump, jump on water, not slip on ice, run faster, have a yellow body, have a super buster shot, electric Z-Saber and be able to auto-charge.
Ultimate Difficulty Setting
Successfully complete the game after all the hidden discs have been collected. Then highlight the 'New Game' option at the main menu, hold R and press Start.
Unlockable List
Beat the game to unlock Zero's mini-game.
Select a game from the Mini-games menu at the title screen.
Complete all missions with 100 points:
Fefnir Mini-game.
Use Zet Zaber for the whole game and beat the game with S rank: Harpuia Mini-game.
Complete every mission with 100 points: Leviathan Mini-game - Use the buster shot for the whole game and beat it with an S rank: Phantom Mini-game.
X Mini-game
Successfully complete the game, then use your cleared saved file to complete the game a second time.