If you have been on Facebook, you should be familiar with Facebook Look back video. They had been shared by so many people that my timeline is full of them. After a while, it looks similar. Now, there is information that you can edit this video.
In the Facebook help page, there is a section on Facebook Look Back. In it, it clearly states that we can edit the movie. There should be an edit button.
According to source, this edit feature is not ready on their 10th Anniversary and therefore, all Look Back video now are non-editable. You can check out the document by following this link.