List of questions about adding media files to Wordpress?

Question

WordPress

Good afternoon, there is a layout of the gallery, video, pictures in a single post. Moreover, you need to make a choice what will be the poster in the blog output (gallery / video / picture) and also to be able to insert any of these "media resources" into the post itself. At the moment there are 3 custom fields: for gallery, pictures, video. Poster logic can be written.
But with the insertion of "media resources" into the post itself, the following questions arose:
* it is necessary to be able to insert in unlimited quantities.
1. How to insert an image using the "Add media" button so that attributes for the link to the image are automatically added (via add_filter)?
2. How to insert a gallery (preferably the default one from wordpress) by changing the template of the output itself?
3. Video cannot be added through this button, how can this be done? It is necessary that the YouTube video identifier be displayed in the frontend and attach a template to it.