How to get Robos
HADRON: Defeat all four Greybaum boss data in the undergound, then fight and defeat the guy below your shadow self, then you will have Hadron and his parts
MISTRAL: Defeat Eddy the second time in Numero Uno's club house after defeating all the grudge matches (you will be able to do grudge matches after you beat the Robo Cup, and yes, the second one, not the one controlled by the Greybaum Syndacyte).
RAY: Defeat Liv right after you beat Eddy. When you beat Liv, you will receive not only Ray, but the last legal gun, which is long range (this gun is not available in any parts shop).
MAJEL: Go to the very front of the Numero Uno's club house after defeating about a dozen grudge matches (the exact number varies) and defeat the guy standing there. Defeating him will net you Majel, Indigo Gun, Indigo Bomb, Indigo Pod, Indigo legs, and the dark commanders mark, which is a bracelet. The robo and the parts I just explained are illegal, and if you defeat some one with an illegal part equipped, you will not earn any stars or exp. from the CRA. After receiving the dark commanders mark, go to Bayside and enter the very bottom left corner house. Talk to the man, and he will show you a secret passageway to the underground, which is the hide out for Greybaum. Illegal parts will be available in the parts store. Here are the prices;
Illegal Robo: $500
Illegal Gun: $300
Illegal Bomb: $200
Illegal Pod: $200
Illegal legs: $200
Illegal and NON-Illegal Stages: $200
Get Hiykou Body
After you beat the Robo cup, go to Dennis's club house. Talk to the boxes up the stairs. Out will pop some kid. Defeat him to get the body Hiykou.