How to login Separately in each blog?

Try using anonymous windows in your browser or separate log ins. For e.g. I’m using Chrome and I can set up different browser accounts with different emails and passwords. It’s kind of a cheat-solution, but it works fine:)

WordPress Header Not Showing on Sub Pages

My guess is your Head navigation is not called in header.php check you file page.php and see the lines following <?php get_header(); ?> if the lines below introduce header navigation either move them into header or copy them into same location in your single.php file

List all blogs a user can admin [duplicate]

This solution works for me: $user = get_current_user_id(); $blogs = get_blogs_user_can_admin($user); function get_blogs_user_can_admin($user) { $blogs = get_blogs_of_user( $user, true ); foreach($blogs as $key => $blog) { switch_to_blog($blog->userblog_id); if( !current_user_can(‘manage_options’) ) unset( $blogs[$key] ); restore_current_blog(); } return $blogs; }

WordPress Multisite

Yes, Multisite is your best choice, you can share plugins, themes and users between websites if you want, also you can have some plugins, themes and users retricted to some sites only. Also you can have top domains for every site into the multisite.