The first buds will appear at arounf 3 weeks of flowering when the pistilles are plentyful. You dont wanna be picking the buds untill the plant is mature in its flowering stage otherwise the THC wont be at its maximum.

You can re-veg a plant after harvest, but its probably easier to take clones before flowering because then you know they are deffinatly female.

Who told you boiling roots will give a higher THC content? That's the funnest thing i heard for while, but forget it. It's bullshit, the THC wont differ at all from it.

And no, cannabis can only be bred with cannabis..