It gives plants all the micro nutrients it needs to succeed. All that good stuff from the periodic table. But yeah it's a soil amendment, you mix it with your soil.
You should be okay, a little early will still give you kickass smoke. The reason you can't grow despite being a medi patient is, ordinance against growing in apartment?
With no preflowers you can't tell sex.
You can flip now if you want, it wont matter. After you flip, about 1 to 3 weeks you will see pistols. Make sure there isn't light leaks, flowering is more stable that way.