question # 1
pre flowers mean the plant is mature enough to bud it dosent mean you have to flower the plant now you can wait just keep the plants in the vegitive cycle (24/0)

question # 2
do some searches on LST (low stress training) or topping,pruning also you might want to look up some info on the "fimming" tech of topping it might help increase your yeild

good luck-Bomb