That will depend on your nationality and where you are coming from. Generally though, for any international travel you should have a passport.
Yes you do. If you leave out of state you need a passport
yes
No. There is a common travel agreement between Ireland and Britain.
Yes, your passport.
If you are from another country yes. But if you are just from another city in Ireland then of course not.
No sorry
Yes, you need a passport to fly internationally.
Yes, you need a passport to fly internationally.
Yes, you need a passport to fly out of Tijuana.
Yes they do need a passport for Northern Ireland
Yes, babies need a passport to fly internationally.
When you enter a country, you have to have a passport--even if you are a citizen of that country.