1)no one know
2)never? if your expense are 0 then you will always be profitable... but, no power costs? Your parents pay the bill? Because well free power doesn't exist
3)Both, if you use the right miner. Problem, cpu mining is so slow that is almost useless. My quadcore make like 20mhash/s while my gpu make like 320...
4)yeah. Remember, always pay attention with your wallet, backup it and pay attention to virus and whatelse
5)dunno
6)no one know