I have one more fairly simple question, which I can ask on the main site if desired. Is there a function to retrieve the site's URL including the front base?
After Site Name: The Final Chapter it would appear that that name "WordPress Answers" is dead, but it survives in the cross-site promotion ads that SE shows in the sidebar. I saw this one just now, on Mathematics.
there are also few ways to restrict cheaper plans other than "less sites" without making them complete crap and multisite is essentially unlimited sites in WP context
@TomJNowell About your comment on the book on GitHub. Have you seen eric andrew lewis documentation project on JavaScript and WP? Somehow I can't find a license. Maybe someone should open an issue on that question. /Cc @Rarst