you cant get them all from one Pokemon game you need to trade with all pokem0on games to get them all
Pokemon HeartGold can communicate with all the DS Pokemon games. :c)
I put a link to a guide all about legendary pokemon in HeartGold in the related links.
You catch them all....
no
you get all the Pokemon
Nope problaly not!
Yes.
There is no best Pokemon on Pokemon HeartGold.
No, you can't get all of the Legendaries in Pokémon HeartGold although you could trade all of the Legendaries in.
there is no Pokemon Mansion in Heartgold.
you throw pokeballs at them
migrate and trade