prevent onbeforeunload to close page in any case

You can't outright prevent a user from leaving the page (This would lead to much abuse on spam/advertisement sites who try to get you to stay on a page), but you can show things such as a window which causes a confirm prompt to the user. Have a look at Prevent a webpage from navigating away using JavaScript which can lead you to the right direction of what you're trying to accomplish.

There is no way to stop browser to close. The browser doesn't allow you to do that.