There are no cheats, but the easiest way I found to get money, was to enter the Grand Prix and come first each time. And if possible. Enter with the boards that allow up to 250 rings each time.
The quickest way to earn rings is to use the Gambler in the Ex World Grand Pri and win first place, through it's difficult. Aside that, the quickest way is to use the gear you feel most comfortable...
Hyper Sonic is a more advanced version of Super Sonic, that was only ever in one Sonic game: Sonic 3 & Knuckles for the Genesis, he is not in Sonic Riders or any other Sonic game. As for Super...