You can't. Sinnoh is only available in Pokemon Diamond, Pearl and Platinum versions which are set in sinnoh.
sinnoh
you cant get to sinnoh in heart gold, but you can find the gym leaders from sinnoh.
First Sinnoh theme: Diamond and Pearl Second Sinnoh theme: DP Galactic Battle Third Sinnoh theme: DP Battle Dimension Last Sinnoh theme: DP Sinnoh League Victors
there is no sinnoh region
No there is no way to get to Sinnoh.
you can't get sinnoh in heartgold.
Registeel is not in the Sinnoh Pokedex. :)
You have to have arceus to get to sinnoh but only once
mossdeep is not in sinnoh
u get 134 Pokemon in sinnoh
Finneon is 134 in Sinnoh Dex
Sinnoh Sound is a Radio Channel that lets you catch different Sinnoh Pokémon depending upon your location.