The easyest Pokemon is scizer and the hardest Pokemon is milotic.
You can't really go further then that. The pokemon league contains the toughest trainers in pokemon platinum.
nothing
fish with the super rod at the pokemon league
North of the Pokemon league (Take the seabreak path)
Beat the Pokemon league again and go back to spear pillar and you will see dialga again.
In Pokemon league
I would use rare candies. Or, train in Victory Road.
jynx ..
no
go to the Pokemon league
Never mind, I'll ask again... Well the best way in Pokemon platinum if u want a strong Rhydon is to look inside the cave before the Pokemon league.
no
they are in the Pokemon league.
use the move nuclearbomb
Pokemon league.
at the city of the Pokemon league
No. You need to beat the Pokemon League IN the Platinum one.