Hello all. Not sure if this is the right type of forum to ask my question but going with it anyway. My child is aspiring moviemaker; thus, he's learning the ins and outs of using iMovie. He's works in iMovie via external hard drive on a MacBook Air (Mid 2011) [Yosemite 10.10.5] with iMovie 10.1. While working on a project with a friend, he plugged his external drive into friends Mac which was running iMovie 10.1.9. Now he cannot open iMovie file on his computer because it was autosaved to the newer iMovie version 10.1.9. I imagine one work around is to upgrade the operating system to the level that 10.1.9 will work but I don't think that will be possible on a Mid 2011 machine. Any insight into how I can help him will be very much appreciated. Thanks, in advance!!