Can I separate cream from powdered​ whole milk?
I don't think you can get cream out of your milk - it would be homogenized by the process, and people would want their milk to be smooth and not separate out so they would take precautions against such a thing in the manufacturing.  Also, a lot of the powdered milk I see sold is skim milk powder, you should be very sure you're getting full fat powdered milk even to try. 

You might be able to get butter, but as far as I know butter from whole milk would be a lot of work for a relatively low yield (one reason cream is preferred, and butter was historically often made from soured milk - it was easier to get butter after culturing).  Though it looks like powdered milk can be used in cheese-making (according to CMB92's link), for increasing yield of cheese or making fresh cheese (your mozzarella could qualify).

On the other hand, if you are buying in bulk, you might contact the seller and see if you can't get some packages of powdered cream along with the milk.  They are likely made by the same manufacturers, and same processes, so it might be possible to substitute for part of your bulk order or else purchase additionally, or even inquire about other powdered products (buttermilk, sour cream, butter powder, etc).  I've used powdered cream before...it can be a bit tricky to work with but, at least with the brand I got, you can make even whipped cream, and also butter - we almost did, from overwhipping the cream.  And manufacturers recommendations usually include uses for ice cream and baking, although you will want to check by the brand you buy, since some recommendations differ.  You can fortify your powdered milk for making cheese with, if you want higher fat.  

And, heavens, I think it would be easier to have two or three packages to scoop out of rather than trying to reconstitute and separate the cream out of your milk (and store it up for separate uses).  You might even be able to make skim milk powder work, if that is what is available, by supplementing it with cream powder to make a "whole milk".