Make a video in iMovie and then record it with the Instagram or Vine apps?

Will this work? If I make a little movie in iMovie, can I use the recording apps on Instagram or Vine to put it on their systems? There's some complicated editing I want to do and I couldn't do it on their apps to begin with. I was thinking of setting up my iPhone and just recording the finished movie with the Instagram or Vine app. I appreciate your help.

I also edit my IG videos on this app call Splice. Most of the editing apps let you save your stuff to your camera roll. So from Instagram, I choose the option where you can upload straight from your camera roll. I don't really know about Vine lol.

Hope I help you!