Is there a way that we can change wordpress user id?

simply change the autoincrement number in your table settings in phpmyadmin to 387100 and it will start and go ahead with 387101, 387102, and so on. As it automatically counts +1 when adding a user, this is the most efficiant and easy way to do it without changing any code.

Unique wordpress multisite requirement

You would do this by editing the site in the network admin, and setting the sites URL to subsite.main.domain, WP doesn’t force you to have everything as a direct subdomain, you could even put completelydifferentdomain.com as the URL and as long as your server is set up to route requests to WP from that domain … Read more