you can flower a plant as little as you want....its stupid to do that but your plant is perfectly big enough and you can flower it....I only vegged mine for 4 weeks and it wasnt to much bigger than yours. (they can double in size during flowering) mine are in 1 week flowering and i cant believe how much bigger they have gotten...)...some people are idiots, and shouldnt give out info.....
Normally if you went from flowering to vegg stage it could take UP TO 2 months to see new growth...I am pretty sure you dont have to wait to put it into flower again, but im not a pro so....pro's shine some light.