Yes they can, most of the apps support MAC and WIN OS. For details google the system requirement of the apps you are interested in, to be better informed about the computer configuration that you should buy for a smooth experience
Sure they can. IMO, you get more bang for your buck with a good PC workstation than you do with a Mac. But other than price difference, they are mostly interchangeable. Don't scrimp on HD space and RAM. You'll need plenty of both.
Nancy O'Shea, Adobe Product User & Community Professional Alt-Web Design & Publishing ~ Web : Print : Graphics : Media