iMovie support 360 videos
iMovie for Mac support 360 videos
iMac, macOS Sierra (10.12.3)
iMovie for Mac support 360 videos
iMac, macOS Sierra (10.12.3)
I haven't worked with 360 video, so can't be totally definitive.
I downloaded a 360 video from Vimeo. Although the movie played in 360 when streamed from online, it would only play flat (not 360) in the VLC app. I could not get it to import into iMovie 10.1.8. My conclusion, based on very limited experimenting, is that iMovie does not support 360 and that you would need to download a special app to play it in 360. You could dry downloading some 360 samples from the internet and see if you can get it to work.
-- Rich
iMovie support 360 videos