I'm assuming you mean in Platinium since Dialga and Palkia are main in their respective games.
In Platinium you need to gain the national Pokedex (so see all Pokemon in the normal dex which is pretty easy if you battle every trainer and visit Solceon's Ruins.) The find the orbs (Adamant - Dialga, Lustrous - Palkia) for the relevant Dragon in Mt Cornet. Taking it to the Sky Pillar will bring forth the Dragon who's orb you have.
It depends on which game. you can catch dialga on pearl with a code
No, but you will be able to catch Palkia, Dialga or Giratina.
The place where you capture dialga or palkia depending on your game mascot
They are both equally powerful. It just depends which game you have for which one you can catch. Dialga is based as a controller of time and Palkia is the controller of space.
Dialga and Palkia are unobtainable in Black 2 (or any other game in Generation 5 (BW, BW2))
Dialga, Palkia, Arceus, and giratinaare not in this game
you get dialga in Pokemon diamond--and no, I caught both my game's fine...
you have to beat the game in order to catch them, so when you do, you can do what ever you want
you have to catch dialga or palkia depending on the game
Once you catch Heatran you've finished the game, unless you are still to catch Dialga, Palkia, Giratina, Mespirit, Azelf, Uxie or Cressilia. You can also fill in your Pokedex. Basically, the main storyline is complete.
in dimond/pearl you go back to spear pillar to get them then you give them to palkia/dialga depending on which game youre playing (dialga in diamond/palkia in pearl). in platinum you use them to summon palkia AND dialga to spear pillar.
No, Sapphire is a 3rd gen game. Dialga and Palkia were introduced in the 4th gen games.