It is in the forest.
It's in Blackthorn city
That is impossible in Pokemon HeartGold and SoulSilver.
Aura Beam is in Pokemon HeartGold.
No, you cannot sell eggs in Pokemon HeartGold.
You need to mate the Pokemon with a Ditto.
to get celebi
It's in Blackthorn city
The gs ball.
Celebi is found in the Ilex forest near the 2nd Gym, at the shrine
You must have the pichu from gamestop, and take it to the shrine in the ilex forest.
ilex forest
You have to have a special (Wifi event) Pichu, bring it to the Ilex Forest Shrine. Otherwise, breed Pikachu/Raichu.
it can be used to obtain celeb without gameshark codes, although an adapter is needed for it whcich u could only obtain from an event held in America
There is no best Pokemon on Pokemon HeartGold.
there is no Pokemon Mansion in Heartgold.
You must get the Pikachu-colored Pichu and transfer it to HG. You will get the Spiky-eared Pichu if you go to the Celebi Shrine in Ilex Forest.
It's behind a waterfall. If you have a CELEBI you received by Mystery Gift and talk to the shrine the room might become "useful".