You cannot get a Gigear/Klang in Pokémon HeartGold. This is because Gigear/Klang is a fifth generation Pokémon, and was therefore never coded into Pokémon HeartGold. According to Pokémon HeartGold, Gigear/Klang does not exist.
You cannot get Dialga in HeartGold version.
you can't get sinnoh in heartgold.
They are not in Pokemon HeartGold
Hoenn is not in heartgold version, only johto and kanto are in heartgold, hoenn is in emerald
HeartGold is the correct title.
you can catch lugia in whil islands in heartgold
Shadow Lugia is not in HeartGold.
There is no TM transform in Pokemon HeartGold
In heartgold please :)
You have to trade it to HeartGold from P/D/Pt
Only by trading a Squirtle to HeartGold.
there is no Pokemon Mansion in Heartgold.