Answer:
Well one cheat is that when the warning screen telling you to put and tighten the wrist strap hold down the 2 button and you will have unlocked the practice court for tennis [the court you play on is on hard so be careful it's a lot harder than normal]. this cheat will only work for one match so if you want to play again you will have to start your system over [but you can't hit reset or it won't work].