after you beat them your free to do whatever like catch legendary Pokemon and get your trainer card to change color by getting stars, and you can go to the battle tower!
You then have to beat Cynthia
an level hundred
No you don't.
Then you beat them:)
His lab.
beat the elite four!
after u beat the elite four
You have to migrate them, which I think can only be done when you beat the elite four.
beat the elite four and become champion
yes there is it is...... 5ty57djsl
Well,Level 70-100 Is A Good Level To Beat The Elite 4.
When you beat the elite four in Diamond/Pearl you can migrate Pokemon from your GBA games.