Unfortinutlly you can not legitly catch Palkia in that particular game, you can migrate/trade it from pearl or get it on the GE.
in the ruins of Alph
you must get arceus at lv 80 + and go in rains of alph in the house.after you must select palkia dialga and geradina at lv.1
Yes
With a Poke Ball
in MT.Mortar
get an arceus and take it to ruins alph
its when you get a dialga palkia or giratina egg
Trade from Pearl or HeartGold/SoulSilver (Arceus event)
nothing, you just have three legendary Pokemon
You can't GET them, you have to trade them from pearl, diamond or platinum.
No, You must be a newbie Trainer the legendary Pokemon you can find in this game are, Articuno,Moltres, Zapdos, Mewtwo, Girtiana,Dialga,Palkia(only if the event Arceus Was obtained), Suicune, Entei, Raikou, Latias(heartgold), Latios(soulsilver), Ho-Oh, And Lugia
You can find Palkia in the spear pillar on the to of Mt.Coronet