It would have to be
Garchomp cause of its slick speed and great attack
Tyranitar because its got a great defence and offence
And Ditto because it can transform into any other Pokemon (including legendarys with out been classified as one itself).
you can't unless you have AR
i think you mean Dialga
you can find legendary Pokemon by using your Pokemon tracker
All, provided you have seen them.
uxie azelf dialga, mespirite, girantina and heetran
the legendary Pokemon in diamond and pearl are dialga and palkia.
That is impossible without hacking into the game, and I strongly suggest you do not. Legendary Pokemon have ridiculous high stats and will just lessen the fun of the game. The normal starters can be stronger than legendary Pokemon if you train them and give them good moves, so why have a legendary? Besides legendaries are really slow in levelling and you will most likely end up underleveled.
No, a Bidoof cannot evolve into any Legendary Pokémon in Diamond.
Heatran
a lot of legendary Pokemon
Dialga
you cant unfourtanately
arceus
you can't catch it because you already beaten the legendary
its impossible without cheats
By trading the other starters with other players of Diamond or Pearl.
no