1) You cannot lose always battles, you have to have have a clean record, you have to win many, many times straight in a row to be reconized. If you do lose you have to start over again so be carful.
2)Nope, if you mean by no cheats then a Nintendo Event.
3)There is no such thing as a best Pokemon, everything has weaknesses, but my best bet would have to be Salamace or Kingdra.
Yawn - what is there to say?