It is known as the "Belfast Agreement" and also know as the "Good Friday Agreement".
The sea that separates Ireland and Northern Ireland from Great Britain is called the Irish Sea. The area of sea immediately north of the Irish Sea is called the North Channel, and separates Northern Ireland from Scotland.
Before the separation of the Republic of Ireland and Northern Ireland, it was called just "Ireland".
The country you are referring to is called Northern Ireland, which is part of the United Kingdom. The capital of Northern Ireland is the city of Belfast.
Ireland owns itself. It is an independent country. You are confusing Ireland with Nothern Ireland, which are different things. Northern Ireland is part of the United Kingdom. Ireland, officially called Éire and sometimes called the Republic of Ireland is independent. Both Ireland and Northern Ireland are on the island that also has the name Ireland.
'The Troubles'. Ulster
northern Irish
They were nationalist.
Peat or turf
Ulster has 9 counties. Only 6 of them are part of what is called Northern Ireland. In fact, the most northerly point of all of Ireland is in Ulster, but in one of the 3 counties that is not in Northern Ireland.
There is no special name for Northern Ireland and Scotland together.
Ireland is an Island split into two parts. The Northern part is called Northern Ireland and is part of the United Kingdom of Great Britain and Northern Ireland. The rest, called Eire, or sometimes Ireland, is a separate sovereign state. (Until the early 20th Century, all of Ireland used to be part of the UK.)
Scotland, England, Northern Ireland and Wales are known as "constituent countries" of the United Kingdom. Scotland and England were kingdoms in their own right, Wales used to be called a principality and Northern Ireland a province. Ireland is both a state and an island, the island comprises of the state of Ireland and that part of the UK called Northern Ireland.