Well... not sure have not been there in a long time sorry
You can only get Dialga (Steel, Dragon) in Diamond. In pearl you get Palkia (water, Dragon) found on top of Mt. Coronet, and part of the main mission.
In order to get to Sunyshore, you must complete the part of the plot that involves capturing/defeating Dialga/Palkia. To do that, you have to go through Mt. Coronet. I'd suggest getting a walkthrough of the mountain.
the northern part of mt. coronet at all times (the part nearest snow point)
there is no part like that in Pokemon diamond
The part where Pokemon lives
For Pokemon platinum, you have to beat the game, then get an adamant orb from Pokemon diamond. It's at level 70. For Pokemon diamond, it's part of the story. For Pokemon pearl, you have to get one from diamond.
a coronet is part of a horses leg...
a coronet is part of a horses leg...
Well, in Diamond and Pearl, go to the part of mount coronet west of celestic town. Click A on a boulder to move it.
If you cannot enter Sunyshore City because the guy talking about a blackout is blocking your way, it is because you have additional battles you must complete and Pokemon you must collect before entering that part of the game. Go to Mt. Coronet first and complete that part of the game and you should be able to end the blackout.
If you watch a Pokemon video go to the last part
because it is part of the storyline.