You will find timetables at the Iarnród Éireann website below. It is the train that runs between Westport and Dublin.
Connolly Station - just in the north inner city of Dublin
Yes. Trains going from Dublin to Galway and from Dublin to Westport, go through Athlone. Both leave Heuston Station in Dublin. There are lots of services each day. Check the Irish Rail website from the link below.
You can take the train out of the station, but you can't take the station out of the train.
Trains from Waterford go to Heuston station in Dublin. There is a light rail link between it and Connolly Station.
Get a Luas tram to Connolly Station and from there get the Wexford train.
The nearest mainline station is Connolly Station. From there you can get a tram to the stop called The Point which is the nearest.
Kings Cross Station
SMS
If you are talking about Euston Station in London, to Dublin port, then it would be an international journey so you may need a passport. It will depend on your nationality. If you are talking about Heuston Station in Dublin to Dublin port, then it is a journey within Ireland, so that journey itself would not require a passport, but you may have needed one to get into Ireland in the first place.
The conductor.
had left.The train had left the station on time.
You would need to get at least 2 trains, one from Belfast to Dublin and one from Dublin to Cork. They are at different stations, so you would have to travel from one to the other on arriving in Dublin, which you can also do by rail. The whole journey from Belfast to Cork could take between 5 and 6 hours, depending on the times you travel and the connections for the departure times.