Let's first establish if you're talking about Blocs or Hype. If you were using Hype, I wouldn't recommend using a Youtube video, but using a regular MP4 video file. It will be much easier to detect when the video is complete and to perform some action (like show that Ophelia URL). The bottom of this post has info on that process: Sync Timelines to Video & Audio in Tumult Hype. That does involve a small snippet of code, but it's not much.
If you were using the Youtube embed, you would create a single scene with everything all setup, and then create additional layouts as you want. These are similar to breakpoints, and the contents of each layout is different, with entirely different elements. But if you start your content on a single scene and add layouts later, this will use the first scene's contents as a starting point. (You could also use Symbols for shared components across scenes).
If you're in a rush for getting this all done and wrapped up for multiple browser support, you may want to hire someone, but all the answers can also be found if you have time and patience.