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I had trouble finding iMovie in the app store. Searching for it didn't work. I had to go to an article online to link me up to itunes to get it. Even after I downloaded it, I am not 100% how to use it. I haven't seen the other editor you speak of, so sorry.
 
I couldn't find it on the App Store on the iPhone, but I was able to find it in iTunes on the desktop. Downloaded and synced.
 
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