How to add a full screen button to Youtube videos that are added to the site using "share"?

Question

YouTube

Hello! The task is to make the button full screen for those videos that are added from youtube with the help of "share". It is known that in order to cheat the visit, the youtube developers removed this button. Now only through the HTML code (iframe) you can insert a video with this button, but this is not suitable, since you want the video to appear in a pop-up block after clicking on the image. I need to shove the link of this video in <a href="(ну то есть сюда)"></a>
So, adding this video through an iframe does not solve this problem, therefore the option is not suitable. I tried to pull out the link to the video from the iframe code, but this link does not work. Therefore, it is necessary to somehow make it appear by adding it with the help of "share". How can this be done, please advise?

On the screenshots: inserted from above using "share, below through iframe.