There is this action which you could hook into: woocommerce_order_status_changed() The 2nd and 3rd variables returned are the previous ...
Which seems to answer Question 1, which is what leads me to believe if WooCommerce or a payment gateway changes the order status ...
WooCommerce Hooks for Order Status Changes. GitHub Gist: instantly share code, notes, and snippets.
Want to change the WooCommerce Order Status so it automatically says
Now that you're viewing your order status list, you'll be able to edit core statuses, ... This changes the order in which they're displayed on the “Edit Order” page and ... Most of the standard WooCommerce hooks for editing email contents are ...
Yes, you can use the woocommerce_order_status_delivered hook – this is general WooCommerce Hook when order status changes to delivered. For example ...
do make available a list of all WooCommerce actions, filters and hooks.
Transactional emails are a key piece of your order fulfillment process. They update your customers on their order status, provide valuable information
Add a new field to the checkout; Add that new field to the order.
WooCommerce Code Reference