1) there is no real minimum. most usually wait until you get at least a couple of nodes worth of growth. probably at least around 2-3 weeks.
2) most people usually don't top during flowering just because there won't be much time for the growth of the plant into 2 colas. i would do it at least a week before flowering to give the plant time to grow out the colas.
3) about 2 weeks or more just to get the root system established and more growth on the clone.
