Switching from sub directories to sub domains is not easy. Start by looking at https://wordpress.org/support/article/multisite-network-administration/#switching-network-types, besides that, you might also need to run search + replace queries on the database to update the URLs on the content, and re-save the permalink structure.
Is there something I need to know in order to use WordPress on foreign (Swedish) TLDs?
wordprees multi-site in user panel add filter
What is better way to sync wp multisite woocommerce products
How to sort posts by active category in WordPress?
Certain lines added to our wp-config.php file are being removed, every day
Installing wordpress on a subfolder of adsense approved domain
unlogged users do not come with nothing. so it’s easy: no-where. for the comments scenario you describe, wordpress creates cookies. cookies are fairly well integrated with PHP, you can find out more about that part of PHP here: http://php.net/manual/en/features.cookies.php Have fun!
You may need to set “AllowOverride All” in your apache config, for the Directory block for the server root, or root of your WordPress install. Here’s what the relevant block looks like on a *nix system; things will probably look a little different on Windows: <Directory /var/www/> Options Indexes FollowSymLinks MultiViews AllowOverride All Order allow,deny … Read more
See this post: http://wpmututorials.com/known-issues/did-your-users-theme-options-and-widgets-page-disappear/ Basically, pick a different cap until it works. Also see: http://codex.wordpress.org/Roles_and_Capabilities