1. at present,because of the hot days, I usually shut down my machine when I was at home and turn them on when I'm off, let's say 12hours/12hours, is this mean on the long run i'll get half compare to let the machine run 24 hours/day without stop
It would be so if difficulty would not change. If it grows, you'll get less then 50% as your time-average of the mining difficulty would be higher. Yep, no time to waste

2. I got 3 machine, which will be better,pointing the 3 machine to one wallet adress or 3 different adresses, or just the same
Just the same