Can ricotta be made from powdered whey?
Disclaimer- I haven't tested either so this is guesswork. I have made ricotta with the whey of a variety of cheeses but never these particular combinations. If someone has already tried these their answer would carry more weight.

Ricotta works because some of the water soluble proteins in milk don't bind up with the cheese (of whatever type) unless they are heated almost to boiling first.
Bringing the whey to a boil forces those extra proteins to coagulate and they are strained out.

1. I imagine it might vary from product to product. If the whey was produced just from drying regular whey then rehydrating and boiling should be enough to curdle its proteins. I suspect that its processing includes heating steps that alter the proteins. I would be surprised if this was possible.

2. Many cheeses use rennet but most also rely on acidification of some sort, either bacteria or acid added directly. As with #1 it depends how the paneer was made. If it was made with warm milk and acid then there will be protein left. If it was made with boiled milk and acid then there will not.