Welcome to the challenge! You really shouldn't need to hack in Eevee for FR, due to it being in the Celadon Condominiums. As for getting Eevee in Emerald, you may hack it in, but at Lv.5.
Hi, I might be wrong but because of no Day/Night System in these games, isn't impossible to get the Espeon/Umbreon evoloutions? If I'm only allowed to play through with an Eevee then I don't mind.