you keep playing...
get all the legendarys
I dont know what happen in diamond, but in platinum you can catch ! and ? unowns.
You can catch Rayquaza in your house upstairs after you catch all the legendarys in the game.
Nothing.
then you stop playing then you stop playing
in the U.S.A? Nothing? there are no U.S events for diamond or pearl. Sorry. (In japan its the all legendarys event. You get all the legendary pokemon at level 100)
you find DIALGA, UXIE, MESPRIT, AZELF, GIRATINA that's all I have so far but there might be more. You can get them from events as well. there is also creselia and heatran
The tunnel on top the ruins is accessible.The tunnel is where you catch the ? and ! Unown.
Battle the E4 and they will all come back?
it doesn't happen, there is no glitch, it only happens in the Japanese versions. Plus, if you get an action replay, you can get him and all the other legendarys.
Nothing unless you migrate to diamond or pearl. Then you can get Rigigigas
No. There was a special Arceus event that could be used to get an Arceus , but if you didnt do that, you must get an action replay, or get the the azure flute via mystery gift for Diamond, Pearl, or Platinum. Bear in mind that if you did not do the special 12th movie Arceus event, you can only get one of the Dialga, Palkia, or Garatina that comes out of this event. But also keep in mind you dont have to catch all the legendarys in heart gold to do this event.