"Does this apply to Music? Could the music that I’ve ‘bought’ from iTunes disappear because they lose the rights to it..."
Much of mine has disappeared. Apple say you can download music you've bought as often as you like, but there are weasel words along the lines of 'so long as we still sell it'. Many of my purchases were made when replacing my vinyl catalogue, so there was plenty of 70s stuff with titles like 'Diamond Dogs 2015 remaster'. Once 2015 ended the title of the product on sale changed to '2016 remaster'. At that point if you lose your local copy, you're well and truly stuffed, as I discovered.