Is it possible to take a movie that was not made as a Responsive project and make it into one?

A movie is a video file, right? If so, just insert into a Responsive Slide as a video object and you should be set.

But if you are talking about a typical Demonstration or Simulation project that records in the "stop animation" type of recording, you cannot simply save those as a responsive project. You will have to create the responsive project and add any elements you need.

Cheers... Rick