Video Rewind Button

This line will get all videos on a slide...

var allVideos = document.getElementsByTagName("video");

So when you have multiple videos on a slide you can either do this...

var firstvideo = document.getElementsByTagName("video")[0];
var secondvideo = document.getElementsByTagName("video")[1];

where the number between the brackets refers to your separate videos..
Do notice its zero-based as is quite normal with arrays and things like that.
... or use a similar notation on your allVideos collection...as you already gathered all
videos inthere...

var videotoActUpon = allVideos[3];

This way you can trigger any video on a slide...If the video is on another slide...you need to use similar script on that slide to act on it.

Hope this is clear and helps...if not...share a sample.