About 385km by road.
If you measure the straight line flight distance ("as the crow flies"), the total distance from New Jersey to Belfast is 3,209 miles or 5,164 kilometers.
About 62.
About 69 miles.
The distance between Killarney and Limerick is approximately 72 miles by road.
The air distance from Belfast, Northern Ireland, to Inverness, Florida, is 4,097 miles. That equals 6,592 kilometers or 3,560 nautical miles. I suspect that this questioner is asking about Inverness, Scotland. It isn't possible to drive directly because Belfast is in Ireland and entails a ferry trip to Stranraer. The mileage from Stranraer to Inverness is about 260 miles.
check on google maps
There are no direct trains between Belfast and Mullingar. Such a journey would involve getting at least two trains. One from Belfast to Dublin and another from Dublin to Mullingar.
107 miles
3653 miles.
The distance is about 2,980 air miles.
I find no town spelled as Helensbray. However, it is ten miles between Helen's Bay and Belfast.