Cutting back for overgrowth

I have a plant that has done more then I expected. It is already too close to the light for my comfort. It is from a 10-40 year old seed from a bunch I saved over the years. It is growing next to an autoflower which will be harvested in 2-3 weeks. The plant in question was doing extreamly poorly and almost threw it out but took a chance. Now it is taking over and I need to know if I can cut it back 6 inches or so. If I can, I plan on letting recup a bit then change the light cycle to 12/12. One other thing if you don’t mind and can answer. It has shown pre-flower signs. Wonder how that can be. The pic shows the pre-flower I beleive. If that is wrong, please correct me. Thanks for getting this far, lol. Thanks for any replies. OM LP

She’s just lifting her skirt and showing her sex. It’s OK.

Thanks oldmarine.