How do I get WP site to show in both root and sub-directory

Installing WordPress inside a sub-directory is kind of problematic. Yes, you could modify your .htaccess in order to show your WordPress site on both the root folder and the sub-directory. However, most likely you will run intro troubles later on. Best suggestion is to move your WordPress installation to the root folder.

Run multiple installs using the same wp-admin & wp-includes?

There are different ways to organize it. You could use a single location with core files and implement boot that points to different tables conditionally. You could implement multiple locations and symlink a single copy of core around. Practically though you should consider which issue are you really solving with this? The disk space is … Read more