yes
The benefits of using a night vision rifle scope on your rifle, is that at night you will able to see through the scope. You will be able to keep everything around you dimly lit, as to not draw attention to yourself.
Recommend you contac the CA DOJ and a lawyer for the current legal answer.
You need to tell us which rifle. Chances are that there is some legal way to own it.
18
Depends on where you are.
The minimum legal barrel length for a rifle without requiring it to be tax stamped and registered as a Short Barreled Rifle is 16 inches - that's federal law, and not just Vermont.
You must be 18 to buy a rifle. The stock has nothing to do with it.
none
range of his vision, and, later, of his rifle
That is question for your state laws. Check local legal representation.
Yes
18.