I heard that you can get your crop to flower useing some kind of method I think it might be the 12/12 cycle 12 hours of like and 12 of dark but idk
you switch the light cycle to 12/12 usually to initiate flowering yes. But some use 11/13 as well. Just takes experimentation to figure out what works best for your environment and strain.
yes you can for sure start a plant in flower within 3 weeks using the 12 on 12 off method. its is not necessarily the best idea since the plant is not into full maturity and you will not get as high of a yield or as potent of buds *as you could* but none the less a great method.