No way of knowing,depends on how long you veg, your lighting, and the genetics of the strain you're growing. If you veg for a month and top it, figure 36-48" .You can tell it's a female a week or 2 into flower, generally.
These are very general questions Toker dude. It will take much reading and devotion on your part to dig in and read the articles in this forum to become a true Budacious grower.