Not without trading from other games. In heartgold you can get ho-oh, lugia, mewto, kyogre, and possibly celebi and jirachi through event. Others can be obtained through trading or other means. It is possible to have all legendaries on one heartgold cartridge, though, if you trade from other game. You need platinum, and emerald, and firered or leafgreen.
Almost all pokemon with evolutions can be bred. Legendaries can not though.
the legendaries can be found when you defeated all gyms
I put a link to a guide all about legendary pokemon in HeartGold in the related links.
The cool legendaries you can get in Soulsilver/heartgold are the following: Lugia, Ho-oh, Raikou, Entei, Suicune, Articuno, Moltres, Zapdos, Mewtwo, Latias, Latios (Latios in Soulsilver & Latias in Heartgold), Kyogre, Groudon, Rayquaza (Kyogre in Heartgold, Groudon in Soulsilver & Rayquaza if you have both).
all except unow and all legendaries
No, you can't get all of the Legendaries in Pokémon HeartGold although you could trade all of the Legendaries in.
probably the legendaries"in my opinion btw"
You can try and complete your pokedex, as well as find and catch all the different legendaries.
well after that you have technically finished the game to you can do what you want. When I finished it I caught all the legendaries.
Any pokemon apart from legendaries and ninorians/nidorinos/as and nidoking/queens
yes,but you have to buy the updated version[it will say "Pokemon heartgold and soulsilver compatible"on the front of the box] there great cheats - i got all Pokemon legendaries! -x999 master balls! and - a lot of hard to get Pokemon!
More legendaries like Pokemon Heartgold and Soulsilver.
I don't think you really can. But in heartgold and soulsilver you will see vortexs in that game but no legendaries in them.
his highest level Pokemon is 88 level pikachu, so train around his Pokemon types. i say legendaries!
No, you can't find all the legendaries in Diamond. There isn't a Pokemon game with all the legendaries in it. You can capture 8 legendaries in Diamond, f you want all the legendaries, you'll need to visit events, trade or migrate them.
yes. leavethem in the daycare center and you will eventually have an egg.
All Pokemon in Pokemon sapphire can breed. Except for all legendaries.