Dialga has no evolution stage.
you can't catch dialgas anywere
You are able to obtain dialgas' picture after you encounter it
In the National Dex.
Yes but only if you trade or have an AR.
You canot a dialga egg in pokemon black and white.
When you see Dialga. Look around (I think its south) You'll find it.
Nope. Like almost all Legendaries, Dialga is genderless and will not breed.
you get kirlia as a partner and buy a dawn stone at the kecleon shop or in dialgas dungeon.
Aura sphere lv 90, Roar of time, Flash cannon lv 80, and Earth power
Hayley does not bring any Dialgas to your ranch, so the only way to get a Dialga would be to trade from Diamond, Pearl or Platinum.