If batsman hits a six on dead-ball,It'll be counted in total runs or not? I have seen in a VIDEO that Australian player is hitting a six on a dead ball and Umpire is giving sign of 6 runs. How runs can be counted on a dead-ball?
The video example which you gave involves a ball which should have been called as a no-ball. If it was, the batsman is entitled to hit it anywhere they like. That ball was not dead but because it bounced twice before it reached the popping crease, it was a no-ball.
Once a ball has been called dead, the batsman cannot hit it so therefore cannot hit it for six.