If you want to fill your Sinnoh Dex, look on websites. There are lists of where to see every Sinnoh Pokemon. If you want to fill your National Dex, you have to import them from your GBA games.
yes
Trading.
I believe it is Pokemon Diamond or Pearl
all the Pokemon on route 210 in Pokemon diamond and pearl are ponyta, geodude and if your really lucky you can find onix.
They have all the Sinnoh pokemon, and some more.
trade diamond from Pokemon diamond onto Pokemon pearl
No, in Pearl you can't get Skunky, Skuntank or Dialga and in Diamond you can't get Palkia or Sudowoodo
You trade Magmar from Pokemon pearl,diamond,or platinum to ether Pokemon pearl,diamond,or platinum.
An action replay DS does work on Pokemon Diamond & Pearl I use it all the TIME!
No, you do not need diamond and pearl to obtain all the Pokemon in the national pokedex. You either need to have a friend who has all the older Pokemon, or you could transfer the Pokemon yourself from older games.
THE POKEMON THAT ARE NOT FOUND IN DIAMOND AND PEARL ARE:MANAPHY PHIONE
diamond