Does that include photons? Photons that have travelled the furthest are, by the above definition, at the boundary of the universe - an ever expanding boundary -

Does that include photons? Photons that have travelled the furthest are, by the above definition, at the boundary of the universe - an ever expanding boundary - which they will never exceed. If this is so and you were 'outside' the universe, would it look like a black hole? Does a universe have an event horizon?