If you really need manaphy then you should use this cheat:
9400130 FCFF0000
62111880 00000000
B2111880 00000000
2000A54 00000007
D2000000 00000000
It's a Togepi and Manaphy.
You can only get it on Heart Gold by getting a specific fossil.
No. It is impossible to breed Legendaries besides Manaphy.
Diamond,Pearl,Platinum,Soul Silver & Heart Gold
manaphy can be given to the heartgold game pack by using mystery gift and also completing Pokemon ranger, you should be able to transfer over the manaphy egg, if not then transfer it over to diamond/pearl and trade it to heart gold, you can breed manaphy with a ditto and get an egg which hatches a phionie, phionie does not evolve into manaphy. hope this helped :)
Because its name is manaphy
You can not get manaphy in heartgold/soulsilver. You will have to trade from diamond, pearl, or platinum.
You can get a manaphy in manaphy cave
go to manaphy.com and click on get manaphy. it tells you how to get manaphy.
manaphy
With Pokemon ranger: shadows of almia beat the game. then on the ranger net use wifi to search for the manaphy egg mission. after completing it you can connect shadows of almia to pearl, diamond, platinum, heart gold or soul silver to send the manaphy egg over. it can be obtained after that by speaking to the guy in green at a pokemart.
Manaphy and Blastoise cannot breed. Manaphy can only breed with ditto or another Manaphy.