no legendary Pokemon can breed. solrock or lunatone cannot breed either. that's all i know of but there is probably more
You cannot breed Cresselia. Cresselia is a legendary Pokemon, and you cannot breed a legendary Pokemon.
No, legendaries, but Manaphy, cannot breed with other Pokemon.
No, you cannot breed legendary pokemon...
Darkar is not a Pokemon in HeartGold. Darkrai is a Pokemon, but it cannot be bred since it is a legendary Pokemon. You cannot breed dark type Pokemon, either.
you cannot breed any legendary Pokemon
No, legendary Pokemon cannot breed, Unless you count manaphy which breed into Phione's but they don't evolve into Manaphy
No. Even though Heatran can be male or female it still cannot breed as it is not in any egg group. Legendary Pokemon cannot breed (with the exception of Manaphy, which can breed for Phione).
every Pokemon can breed when they've evolved using a ditto.
no, ditto cannot breed withe legendarie pokemon.
You cannot breed three Pokemon at once, but you can breed charmander with dragonite. Actually, you MAY be able to breed any Pokemon, if they are compatible.
You can breed any Pokemon capable of breeding with a Ditto. You cannot breed them with members of the no eggs group, legendary Pokemon or other Dittos. Actually You Can Breed Manaphy And Rotom (There Legendarys)
Happiny cannot breed as they are a Baby Pokemon, you need to breed Chansey or Blissey instead.