In the sterilization of the fruit juice filtrate, why is the temperature not to exceed 60 degrees centigrade?

Answer 1

What you're describing is "pasteurizing." It's not necessarily sterilizing, but killing the majority of the bacteria and wild yeasts that will affect fermentation. Too hot and you start damaging the delicate flavors of the fruit that you're trying to preserve and impart to your beer/wine/cider. It will be effective, but at the cost of the flavors.
This is one of the reasons sulfites are used. They accomplish the same task without ever having to risk overheating the juice, or even expend the energy (gas, electricity, etc.) on the effort of heating. The drawback, of course, is that there are people who are allergic to sulfites and they would not be able to drink the final product.

Answer 2

if it exceed fruit will get damaged know.....

Answer 3

so you don't "kill" the nutrients