Can keynote remote work on PowerPoint and slide presentations?

A stand alone Keynote Remote App no longer exists.

A wi-fi remote tool is built in to Keynote for iOS, it does not work with PowerPoint.

You could open a PowerPoint file in Keynote on the Mac [ File > Open ] then use the remote function in Keynote for iOS to control Keynote playing on the Mac.

Yes, iPhone can control the iPad and the there way round if required.

As I said I'm my first reply, there is not a separate Remote Control app available to control Keynote.