You can't have an Eevee hero in Explorers of Darkness or Time. In the original Blue and Red Rescue teams you have to have a naive nature. In Explorers of Sky, you have to have a Jolly nature. You can't be a male Eevee in either versions, by the way.
First, you MUST be a girl to get eevee. Then just answer the questions and hope you get eevee. ALSO you can be a boy to get a eevee and if your a girl you will have to be the jolly type and in boy i dont remember. cause im a girl you can get a eevee even if your a boy NOT ONLY A GIRL.