Does not exile other cards of the same name that are on the battlefield. Just from the graveyard, hand, and library.
Scour can target and exile cards that aren't always enchantments, but are enchantments when Scour is cast and resolves (such as creatures turned into enchantments by Soul Sculptor). Scour's exile effect only looks for cards by name, not type.
The copies must be found if they are in publicly viewable zones. Finding copies while searching private zones is optional.