To keep your Pichu from evolving, give it an Everstone. It will not evolve until you take the Everstone off of it.
Give them a everstone or press b when they are evolving ;)
#155 in Hoenn is Pichu.
Put 2 pikachu in the day care
You can't, you have to breed Pikachu.
By evolving Grimer
It evolves by happiness
you have to breed pikachu or raichu
its for evolving pokemon.. eg. gloom --> bellosum
You need to transfer a pichu to xd from firered or leafgreen or ruby, sapphire or emerald to have one.
You can either keep on hitting the B button when it's starting to evolve or you can let it hold an Ever Stone which prevents it from evolving.
Breed (a) Pikachu or Raichu in the Daycare Center to the west of Mauville City.
Unfortunately the only way to get a Flygon in Pokemon Ruby is by catching a Trapinch and evolving it into a Vibrava and then a Flygon.