if the plant you're talkin about is the same plant everyone else is talkin about, you gotta understand that it is basically an annual.. you usually get one harvest from a plant.. hence "annual" its possible to send a plant back into vegetative after flowering but im not sure what exactly your goin for. look up some other high yield techniques.
I don't think so. Make sure you have a female and harvest when she's ready... Try cloning before flowering and if its flowering already then try cloning then revegging. Seeds seem to yield more than there respective clones IMHO. But at least, you know their gender and qualities.
I have had this problem with a few plants that had been abused with their light times. They were in pots indoors for a while. We got her to start budding. for some reason she was put outside and she decided to go back into re-veg. The buds that had grown already died and crumbled off. The fact is you can save your plant through the winter but your not going to get a better yield from it unless it just naturally has a high yield.