If you go in,you can't.(unless you have an action replay.)
Beat all the elite four and there champion
you need diamond and need 200 Pokemon, and go back to the league
In order to become the master of the Pokemon League, you must defeat the Elite Four and the current Champion. You will then become the League Master. However, when you go back to the Pokemon League, you will fight the Elite Four and the previous Champion as though you never became the Master of the Pokemon League.
you can go back and catch: -azelf -Uxie -Mesprit and also a SECOND -Palkia and a SECOND -Dialga
Yes.
You have to get to the middle of the turn back cave (available after beating the league, where giratina is in Pokemon diamond and pearl), and there will be an item and a portal to it
in the back of velicstone
it is on the back of the case.
in the back of the game
No you get to keep it
back to the Pokemon league
Diaruga (actual name, Dialga), can only be found on Spear Pillar on the Pokemon Diamond game unless traded, the same as Parukia (Palkia) in Diamond. If you want to find a picture of Dialga in Pearl, or Palkia in Diamond, go see the old woman/man in the large house in the back of Celesitc town after beating the Elite four and the Champion of the Pokemon League.