For #1, as a convenience, we use our Live Server to launch a mini-web server on your computer. The URL to get to the server is:
127.0.0.1 means localhost or your computer. :20605 is a TCP/IP port. Normally a web server runs on port 80, but you can have web servers run on other ports. We chose 20605 because not much else would use that port number.
If you double-click on the index.html file in the folder, it loads the HTML file directly in the browser and doesn’t run from a web server. For some simple things, this isn’t a problem, but it’s not running in a proper web server and if you have some requests, it may not work exactly as expected. You, of course, can run your own local web server. Or you can upload the contents of the output folder to a real hosted web server for the most practical experience.
You can always go to http://127.0.0.1:20605/ in your browser to get back to your application assuming you’ve not closed the Live Server.