Loop video in iMovie but fade from end scene to start scene with no fade to black or white

The Loop feature in iMovie 10 will not carry over into the shared out movie. To loop a shared out movie you would need to play it with a video player like QuickTimePlayer and do a View/Loop.

One thing you can try is to put a small snippet of your beginning clip at the end of the movie and put a cross-dissolve transition between it and the last clip of the movie. You might have to fiddle a little to get the effect that you want.

Another thing you can try is to share out the movie and then import it back in to a new project as one large clip. Then select it and Edit/Paste it 2 or 3 times (or as many times as you want) into the time line, so that you have repeats of the clip. Put a cross-dissolve transition between each clip. It's not exactly a loop but it will have the same effect as a loop in that the movie will repeat over and over as the playhead progresses though the timeline.

-- Rich