I am still a novice at brewing so take this with a grain of salt but for Number 1, yes add at flame out. As for Number two add the Columbus when there is 30 mins left in the boil, this round will add the hop aroma for the beer. Then Number 3 once fermentation is done add the Columbus for eight days to dry hop. As I said though I could be wrong.
Also interested to know why all three say 0.0 IBUs, does not seem right in cases 2 and 3.