The troubles were almost exclusively confined to Northern Ireland, so it didn't really need to spread to the Republic of Ireland as such. During the course of the troubles there were incidents in the Republic of Ireland and in Britain, but the centre of the problem lay in Northern Ireland. Once the peace process was established there, things improved. The Irish and British governments were part of the peace process insofar as they helped the parties in Northern Ireland to work together and gave them support in many other ways.

The peace process, most significantly including what is commonly known as the Good Friday Agreement, which was signed in 1998.

The Northern Ireland Peace Process, culminating in the Belfast Agreement, commonly known as the Good Friday Agreement.

A continuation of the peace process, co-operation at local and political level, respect and a change in the mindset of the people. This will take time to happen in full, though Northern Ireland is largely peaceful now.

Neither. There is peace in Ireland now. The troubles are largely over but would have been in Northern Ireland.