Select an enemy follower that costs 7 or more on the field. Destroy it and give this follower +2/+2.
QIs the cost of an evolved follower the same as its unevolved form?
AYes, it is.
QIf I can't select an enemy follower on the field, can I still give this follower +2/+2?
ANo. If you can't select an enemy follower on the field, you can't play this follower's ability.