Well done, Mooman, I totally missed the reference, in spite of ample flagging of the cult of St Brigid on the 'Cat.

Regarding 4, I understand that the practice of playing the national anthem at the end of just about every public gathering began during the first world war, when all of Ireland was part of the United Kingdom, and the anthem was "God save the King". When part of Ireland became independent (he said, choosing his words carefully), the practice was continued, using the new Irish National Anthem (Amhrán na bFhiann). The practice was largely abandoned in the 1970s, due to a number of factors. But I'm not aware of any official protocol for when it should be played, as we're generally rather relaxed about that sort of thing.

A "short version" comprising the first four and last four bars is played as the presidential salute on formal occasions to greet the arrival of the President.