Azelf mesprit uxie, zapdos moltres articuno, giritina, dialga, palkia are the one you can catch without an event. with an event there is shaymin, darkrai, arceus.
Beat or catch Girantina
catch them
none
go to this page http://www.serebii.net/diamondpearl/legendaries.shtml this page has all the legendaries you can normally catch in in Pokemon diamond/pearl all other legendaries you have to transfer from a 3rd generation game
arceus
catch one.
Not including the legendaries and special pokemon ( ones that you can only catch once ) feebas is the hardest and rarest pokemon to catch
Gamestop holds an event which has already passed but if you look up the code for the Pokemon modifier you can receive arceus.
Pokemon Platinum because you can catch more legendaries!
If you mean legendaries, then no.
no but you can catch lots of legendaries
g;r;g;g