Not in Heartgold/Soulsilver.
there is no sinnoh region
You can't go to the sinnoh region.
there is no region after sinnoh in Pokemon diamond and Pokemon pearl.
You can only go to the Sinnoh region in the games Diamond, Pearl, and Platinum.
No there is no way to get to Sinnoh.
u cant leave the sinnoh region in diamond or pearl games
There is no sinnoh region in heartgold or soulsilver, it is only Johto and Kanto.
mossdeep is not in sinnoh
It has only the sinnoh region.
A pokedex containing pokemon found in the Sinnoh region.
You cant.
Unfortunately, no. You can only get to the Sinnoh region in Diamond, Pearl, and Platinum right now.