Unfortunately there is no known way to reveg an auto. This is why the early stages are important to ensure solid growth before flower sets in.
Depending on your circumstances, you could try to finish it for novelty, but if you need the space it may be best to start something new.
No, thats it, autos are time dependant, not light dependant.
Grow photoperiod plants, they are far more managable and co-operative.
And yield more, and have better genetics, and are superior to auto flowers in every way.
Autos are not phenotypes mate. You can grow an auto on full light if you want. They run off there own cycle. More than likely it was nothing u did wrong. Some seeds are just runtz. Look at my CBD hydro she got full shape after 4 wks and has stayed that shape and just gotten a bit bigger. Sadly. Since it started flowering, and with it being so 5. She might double in size or maybe another half and put on some bulk. But u luking at at 5-15g dry. Me too. And mine is 8 wks along.