You talk to the following legendaries to fight them.
Ho-oh- Bell Tower
Lugia- Whirl Islands
Suicune- Route 25
Articuno- Seafoam Islands
Zapdos- Route 10
Moltres- Mt. Silver
Mewtwo- Cerulean Cave
Kyogre- Embedded Tower
Rayquaza- Embedded Tower (after showing Professor Oak a Groudon and Kyogre caught at the Embedded Tower)
Latios- Pewter City, Wi-Fi Event
These Legendaries are roaming the regions and are found in long grass.
Raikou- Johto
Entei- Johto
Latias- Kanto
These Legendaries are given to you.
Dialga- Sinjoh Ruins
Palkia- Sinjoh Ruins
Giratina- Sinjoh Ruins
Mew- Wi-Fi Event
Jirachi- Wi-Fi Event
Note that the Wi-Fi Events are in America and Europe until the 31st January 2011
You can't breed legendaries, because they are genderless and there is only 1 of each legendary
you have to put the legendary Pokemon in the daycare with a ditto for a long time and you have to walk alot until you get a phone call.
you can only breed some
you cant breed legendaries
No, you cannot sell eggs in Pokemon HeartGold.
yes at supercheats.com/pokemon heartgold action replay codes
It's not possible, legendary Pokemon cant be bred.
The PokeWalker allows you to walk with a select Pokemon from your copy of HeartGold and if you walk enough, you can capture extremely rare Pokemon (though not legendary).
no you can not have legendary Pokemon eggs unless you went to a Nintendo event
there are many legendary Pokemon in Pokemon heartgold, but the best is HO-OH
I put a link to a guide all about legendary pokemon in HeartGold in the related links.
In HeartGold you can catch Kyogre.
No, you cannot sell eggs in Pokemon HeartGold.
Articuno
mew
I don't think you can refight any legendary Pokemon except the wandering dogs.
migrate and trade
Kyogre is only available for Pokemon: Sapphire on the GBA. Ho-Oh is the legendary pokemon available to you in HeartGold.
No legendary can lay an egg except for manaphy which gives an egg to phione and you can not get manaphy or phione in heartgold
You can't breed legendary Pokemon eggs on Pokemon SoulSilver or on any Pokemon game.
it is not possible as legendary Pokemon are not breedable