What is the reason behind hot water gets Freezes faster than normal water when we keep both the hot and normal water together in freezer ?
This phenomenon you are describing is called the Mpemba effect after a Tanzanian student, Erasto Mpemba, who in 1963 noticed the temperature of ice cream affected how quickly it mix freezed, though the effect had been observed much earlier (the earliest known observation of this was by Aristotle in 4 B.C, though Aristotle probably didn't use ice cream).
While rather ill-defined, the current definition is as follows:
There exists a set of initial parameters, and a pair of temperatures, such that given two bodies of water identical in these parameters, and differing only in initial uniform temperatures, the hot one will freeze sooner.
The Mpemba effect applies only under very specific circumstances, and exactly what these circumstances are as well as the reason why this happens are not fully understood.
You can learn more about the Mpemba effect here (this is also the source of the quote).