The 30th time i fought the champion in platinum, she had Rayquaza! is this normal? It happened on my friend's game too.
This happened to me as well, and no hacks have ever been used on my game. Cynthia had a Rayquaza, and I think it was around the 30th time for me too. It could just be a glitch, or Nintendo making a reference to Cynthia's travels.
She's never supposed to have a Rayquaza. Your game is hacked.