looks like it is starting to flower, but if that is only after you used 12h of darkness, it is probably a photoperiod. The pics show a plant that's been in flower for over 2 weeks, if it is showing pistils at the terminal buds of each cola. When did you give it darknes? if that does not make sense time-wise, then it might just be a XXL autoflower with a long vege.
If 2+ weeks matches up with the 12h of dakness given, don't deviate from that long-night cycle. if not, probably safe to you normal autoflower light schedule.
go up to a appliance store and ask for a refrigerator box, lol... you can cobble together some sort of light deprevation enclosure if you must.