From experience of researching My Wife's Irish Roots, I can categorically say 'Yes' to Your first two questions.
ADD: Irish Middle Names have traditionally been given at a Catholic Baptism, and are usually derived from a Saints Name. The middle 'Baptism Name' will often not appear on the official Civil Birth Registration Document, but can turn up later, on a Marriage or Death Certificate. Ideally You need to view both a Baptism Record, as well as the Birth Registration, to compare the given Forenames.