It’s incredibly hard to understand your post, but from what I understand, you just want to create a transition between the still image and video. With the video being the size of the still image first and then gradually fill the whole screen as circular fade in. Correct?
Check this topic out for help:-
This covers that circle part, and maybe can help you mask the footage so it opens as the circle gradually. Btw, you would have to get duplicate if the video onto one more track to make it work. The first track which is below should be cropped to size of the image. And the other one, that is on upper track should be normal size, covering the canvas, so it can opened with the masking trick.