Allowing logged in users to comment without moderation across a multisite installation

I currently do web admin for an internet community based on BuddyPress and Multi Site, and use the Comment author must have a previously approved comment setting to make it easier for users to comment and not be moderated. All users are vetted before their accounts are created so I know we don’t have spambots.

Initialize WordPress environment to use in a real cron script

I have to run a PHP script through real cron (WP cron being too unreliable). Within that script, I need $wpdb to insert data into WordPress table. But of course $wpdb will not be available as WordPress would not be initialized. Right? So, my question is how to ‘include’ WordPress/initialize WordPress environment to do such tasks? How about
require_once(“wp-load.php”)?

Creating Ajax backend for Specialised Page Template? Should admin-ajax.php be used?

We’re scoping an upcoming project that will require the development of a large php web application within an existing wordpress site – this is for our use only and we’ve no intention of trying to package it for other users; so interoperability isn’t really a concern as long as we can continue to apply WordPress updates as they’re released without breaking our application.