That will depend on various factors, like the nationality of the person and their status in Ireland in terms of whatever visa they may have come to Ireland on and be still using. If they are an Irish citizen, then it is not a problem.
No.No.No.No.No.No.No.No.No.No.No.
Yes they do need a passport for Northern Ireland
If you are travelling from the USA to Northern Ireland, you need a passport to go there. You probably will also need a visa to enter Northern Ireland but you can find this out if you look up the British government website.
It should be fine as it is. As long as your initial marriage is legal, there shouldn't be any need to register it in Northern Ireland. It will be recognised.
No. Northern Ireland is part of the UK, so the visa will cover it.
I am a british citizen living in northern Ireland and I am attending a wedding in Scotland. I intend to travel to Scotland to the wedding by ferry but intend to fly back to belfast. I do not have a passport but do have a Northern Ireland electoral I.D. card - will this suffice as a means of I.D. at the airport.
It depends on where you are coming from As Northern Ireland is part of the UK you will need the same Visa that you would need to enter any other part of the UK. If you are a UK citizen you do not need one
No.
No! Don't be thick! And there isn't any need to write "the" before Northern Ireland.
They will need a visa to enter the United Kingdom in order to enter Northern Ireland.
only if you are going to Northern Ireland, you need a passport to travel between England and Ireland.
none if you are European. There are no border posts