Looking for sex

Im trying to figure out what sex my plant is before I move it outside. I have 1 five inch plant directly under one light and another CFL above two seedlings. I want to see what sex the big one is so I can move it outside, my moms getting nervous with it getting "big".

How tall should the plant be before switching to 12/12?

And does switching to 12/12 and back to 18/6 not cause any problems? I stressed my plants so many times last year and Im just being very cautious this year about stressing them.

Wait until it's big enough to take a clone off of it. Then place the clone in 12/12 within 2 weeks it should show, then you never have to stress your mum.

I am trying to get it outside quick though...