Nothing bad will happen if you under feed you plant, It over feeding or over fertilizing your plant is what you want to watch for.
veg state doesnt really have a time on it you can have a plant veg for a very long time,personal experience ive had plants in veg for up to 5 months, indoor i usually start to flower after 4-5 weeks veg depending on strain.
Flower Time is an average of 8 weeks but it depends on strain look up strains flowering time.going past your plants flower time will degrade buds. you want all Tri to be cloudy white (not transparent) , letting them get a little amber will result in a lil stronger High but dont let em get too amber i like the high i get a 100% cloudy white.
You can sex your plants during flower but unsure when exactly too do it make sure, When sexing plants keep pollen AWAY from other females Unless you want SEEDED buds.
you can top your plant thru out veg as much as you want, personally dont like to do it more than 3x you should try FIM technique, I like to stop training 1 week before flower (12/12)
so they transition into flower full strenght, Although some people like to train em up too the 2nd week of flower.
You should have more light in flowering, many Light schedule's for veg you can do 18/6 20/4 24/0 i prefer 20/4, To Flower you need to imitate Fall 12/12.
I like to use Fox Farm good results and cheap also easy to use very elementary. Results look professional going to be switching soon to something more complex.
If you Have root bound the tip of your leaves will curl down letting you know it has root bound. I like to use the gal per foot rule of thumb. example 1 foot plant 1 gal, 2 foot plant 2 gal etc. I usually keep my clones in a 16 oz cup for a week than switch to 1 gal for 2-3 weeks than switch to a 5 or 3 gal depending on strain a few days before switching 12/12
