Yes same as fire red
Fish using a good rod or better in the water outside of Bill's house.
you dont battle bill
Bill's grandpa (north of cerulean) will give it to you if you show him a certain pokemon.
No, you cannot find cyndaquil in LeafGreen.
U can do it, but I'm not sure how yet. I saw it on youtube! I'll rewrite this answer if I find out.
LeafGreen version does not have Growlithe.
There aren't growlithe in LeafGreen. FireRed has growlithe, LeafGreen has vulpix.
no such thing
That item doesn't exist in leafgreen.
you cant go underwater in leafgreen!!
Piplup does not exist in Pokemon LeafGreen or FireRed.
Go to five island and receive the parcel from the old man. Then go to Bill(after finding the ruby and sapphire) and give him the parcel. Bill will give you the light bulb.