JavaScript в нижней части/вершине веб-страницы?

If you have static html content and a lot of javascript, it can make a difference in perceived page load time since the html will load first giving the user something to look at. If you don't have much javascript, or the existing page content relies on the javascript to be useful, then this is not as useful practically-speaking.

Yes, the page will load the content and render it before loading and executing javascript, and the page will, as a result, load faster.

Assuming you aren't running on a CDN or aren't serving your JS from a separate sub-domain or server, it will load synchronously and force your HTML content to wait until it has downloaded the files. By placing the JS at the bottom of your page before the closing tag, you are allowing the HTML to be parsed prior to loading the javascript. This gives the effect of faster page load times.