Rowan gave you a pokedex for a reason
You can't.
You are always in Sinnoh.
For Shinnoh:493 Isshu:649
The next series is called pokemon black and white
You have to see all the Pokemon in Shinnoh. (You do not have to beat the Elite 4)
transfer the Pokemon from gba game into pal park and capture
no, not necessarily, you do however need the nationalDex which you get for seeing all 150 Pokemon in shinnoh
find em all stupid
This is how you get the Pokemon radar. First once you defeat the Pokemon champion and you see all the Pokemon in shinnoh you go to profecer Rowan and then you talk to him then he will gove you the Pokemon radar.
Probably, it doesn't seem as though there will be any further games after Platinum
no i think ash will go to where Pokemon coleseam took place:)or gale of darkness
You never do go to the Sinnoh region, but U can transfer the Egg there.