Bill,
The starting point should be the original video, MP4 or MOV.
1. No - (if you mean 'stretch' the placeholder to the width of the browser); yes (if you mean stretch the placeholder (video) to the width of the page). You can though create full width and full screen videos with some simple code: Examples here for desktop and mobile:
https://initiostar.co.uk/demo/Video/banner.htm.
2. Yes - but not sure what you want to achieve (maybe a banner video?). You could use a video library approach:
https://initiostar.co.uk/demo/VideoPopup/. This is not a popup on a page; it places the video on its own page and that video is called from the main page. Very useful if the video has an audio track, since this actually stops video and audio.
3. The video should sit on your server and be called from there.
4. No - I doubt it. Much better to have the original video and control of the video.
What had you in mind? You could add a few frames (opening sequence) to the video itself, or you could have an intro fade in /fade out text based sequence aka something like this:
https://initiostar.co.uk/demo/TextFadeEmbed/
Gary
Live example:
https://hypnosis-retreat.co.uk/index.htm