Scotland has a land border with just one other country, which is England. The Province of Northern Ireland is a short distance across the Irish sea. A little further away are the Republic of Ireland and Wales, further away still, to the north and north east are Iceland and Norway. To the east of Scotland lie the Benelux countries, and Denmark.
Depending on where you are in the country its either Wales, Scotland or England.
Northern Ireland then Scotland, Wales and England, These four countries are collectively known as the United Kingdom (UK)
Scotland and England (Great Britain) share an island just East of Ireland across the Irish Sea.
Ireland shares a land border with Northern Ireland which is part of the UK. That makes Ireland the closest neighbour to the UK. Ireland is the offical English language name of the southern portion of the island of Ireland as used by the Government of Ireland and not Republic of Ireland or The Irish Republic.
England shares borders with Scotland and Wales, so they are the equally closest European countries to England. The closest mainland European country to England, which may be what you mean, is France.
Presumably Ireland or Scotland.
No.
The closest country to UK would be Ireland as they share a land border (Northern Ireland is part of the UK). The closest country to the island of Great Britain would still be Ireland as the Northern Irish island of Rathlin and Scotland lie some 15miles apart. However, it is about 20miles from mainland to mainland. The distance from England to France is about 21miles - just slightly further.
Scotland and Ireland
Northern Ireland
united kingdom