The flowers all mature at different rates. So much mis information about autos.
Yes you can regenerate autos.
Yes you can clone autos and go through normal veg flower cycle and get a large yield.
No Autofems do not go into flower and just die.
Like all cannabis it's adaptive .
It flowers based on maturity of the plant Not age!!!!
So if you pinch the tops in vegative you will get a larger plant.
I have seen a beautiful auto clone that finished with a very respectable yield. I have not tried cloning Autos my self.
As for chopping an Auto and putting back to 20 hours. In my case I got a second full size plant! The crop will not be as big but autos from a same strain can have very different phennos. If I get an auto that really impressed me than it's worth it to do regenerating.