With a other Eevee, one of its evolutions, or a ditto.
No, Eevee does not have to evolve to breed.
Eevee can breed with any Pokemon in the Field Egg Group and including Ditto as well.
Yes. Breed a ditto with any eevee evolution and the result egg will be eevee.I second the verdict. The egg will definitely be an Eevee.
eevee
you will get an eevee because a flarion is the grown up version of eevee