im not sure what ppl say is the smallest but ive heard 5gallons for the final flowering stage, if your plants are at 3-4ft that's pretty fckn big.
if the roots are growing upwards that will just stunt the growth a bit bc the water will naturally drain down, which is goin to be away from the new roots, if anything bro, raise the soil level if you can...
they say that for every foot of plant you should use 1 gallon of soil for enough room for good roots, but i've seen some decent plants that were 3-4ft and they were only in 1 gallon pots. but if your roots are comming up then you need to repot quick.
Thanks for comments umm im using a 12 inch wide and like 9 inch downward pot im hoping my plant will grow atleast 2-3 foot u think its possible in 12 x 9 pot
pots are so cheap im not sure why you'd gamble w. something that takes so fckn long to do. if it's a matter of room, then it doesn matter what's possible bc ur limited by room. id just go the store and upgrade bro. but yea, if the roots start to come up above the soil line that's bad.