To get Completion bonuses, do the following tasks:
1. Complete the game on the Normal difficulty setting and you will unlock the Hard difficulty setting.
2. Complete and save the game with both Vent and Aile on the Normal or Hard difficulty setting. Then start a new game with the cleared game file to keep Model X after you get Model ZX.
To unlock Mega Man Zero 3 Bosses, you should have the Game Boy Advance game Megaman Zero 3 in the cartridge slot. Then, bosses will appear during the game.
To unlock Mega Man Zero 4 Bosses, all you need is to have the Game Boy Advance game Megaman Zero 4 in the cartridge slot. You will see bosses from that game appear during the game.
You can also unlock mini-games, just accomplish the following tasks. To play the mini-games, go to the arcade next to the transerver in Area C-2 and press Up.
Crusher-F: defeat any two Bosses.
Mega Crusher-F: defeat the Crusher-F mini-game high score (100 points).
If you have the green keycard, go to the teleporter that is before the C-1 level. Then, enter the level and enter the green door. While you are in human form, go under the gap and get the three items on the right. They will give you an extra life. Now, you can go back to the teleporter, then repeat this trick as many times as you wish.
To unlock Free Birthday Cake, all you have to do is to change the system date to the day of your birthday, then go to Area C-1 and talk to Sherry. Thus you will receive a free Birthday Cake and 8 Health points.