You cant
You don't. On certain days, the radio will play Hoenn music so you can see Hoenn Pokemon. But you can't get the map.
Look on your map.
You can't.
Hoenn is not in heartgold version, only johto and kanto are in heartgold, hoenn is in emerald
You can't get to the Hoenn region in HeartGold or SoulSilver. However, Latias can be caught in HeartGold, which is a legendary from Hoenn.
If you mean Hoenn field on the pokewalker then you have to have 5,000 watts to unlock it. If you mean in gameplay then I have no idea what you're talking about and I seriously do not know
As with the original gold/silver/crystal, you can only travel to Johto and Kanto. Hoenn and Sinnoh are not available. You can open at least one Hoenn themed route in the pokewalker however (I believe I just opened Hoenn field at 10,000 watts) where you can capture certain Hoenn species.
No, you don't get Hoenn, but you get Johto and Kanto
You can't.
To get Illumise, you have to obtain the national dex and have at least 5,000 watts on the pokewalker. You will unlock the "Hoenn Field" route. Then go on Hoenn Field and use the pokeradar. There is a chance you will find an Illumise.
In HeartGold, you cannot enter the Hoenn region however you can find Pokémon that are found in the Hoenn region in HeartGold by playing the Hoenn Sound on the March Channel while you're traveling through routes however the Hoenn Sound is only available on Wednesdays.
You sex lyra