I don't know about movies, but you can definitely lose apps. I used to own a game called X-Plane that I played on my iPad. Then the authors created a new "version" (as a new paid app.) At some point, I reset my iPad and set it up as a new device and there was no way to download the app anymore as it had been removed from the app store. It is still hosted there somewhere, so if you have the backup, it will download the app from the app store, but it is not "findable" so if you have a new device, so sorry.