This has been answered already:
You get an Eevee from a person in Celadon Mansion.
yes
celedon city
you need to trade from Pokemon leafgreen or firered
eevee and staryu
Glaceon doesn't exist in firered.
you can by evolving eevee but not by capturing
get a girlfriend
No, but if you have a girl or a ditto you can breed it and get more eevee's.
Eevee is not available in Pokémon Sapphire. Eevee is available in Pokémon FireRed and LeafGreen and you may be able to trade it from LeafGreen or FireRed to Sapphire.
(firered) get eevee in celadon and give it waterstone.
someone gives you one eventually.