How long ?

Well most autos take 4week for veg and anywhere from 8-10 weeks flower. If its a sativa she's going to be around the 10 week flowering time. Looks beautiful thou :). Best wishes

18/6 or 20/4 lights are optimum for autos. 40% - 50% RH during flower. There are different opinons on when to harvest, but all say after the Trichomes are milky. Trichomes go through the stages - Clear, Milky and Amber. It depends on the strain and what affect you are after - Milky = head affects / Amber = more body affects. Milky = Sativa Amber = Indica I generally look at the middle of the buds Trichomes (not leaves) and aim for 30% - 40% - but this is personal choice. Again it depends the strain but 84 days is a rule i follow to say autos are generally done.

2-3 weeks or when there are 95-99% brown pistils. More pictures under normal light is always better.

So autoflower plants don't follow light schedule. Doing 12 12 on them literally destroys their potential. 18/6 or 20/4. Looks like 3 to 4 weeks left. Need better pictures to tell. Preferably not under a grow light.

I read that 12/12 for auto is not good u will have small buds, I will suggest to do 18/6 btw that a early flowering stage so u have like +4 weeks