There's a thread here ... 12/12 from seed or something like that ... I haven't read it either, but I think it will answer your questions, as I've seen others refer to it several times.
I've been meaning to read that thread, maybe I'll do that now.
when the plant starts to alternate nodes it is a sign of maturity "ready to flower"
you don't have to wait.... but some would argue you get a better yield if you do