I agree with Allan C, but since AlasdairUK has set a precedent of answering your multiple query, I'll add a bit also!

You'll find more discussion about Johnny has gone for a Soldier if you do a forum search for the discussions of Shule Aroon / Siúl a Rúin. The song in its many variants has been used from the aftermath of the Jacobite wars, circa 1745 to the American revolution and the American civil war. 'Johnny I hardly Knew Ye' seems to me to be quite a different song, not another version of 'Johnny has gone for a soldier'
I thought 'Red is the Rose' was a recent song, by Tommy Makem, but probably he adapted it from an older song, because there are two versions in the database and one is attributed to the singing of Joe Heany.