Where can I find a list of all the shortcodes? Also, is there a way to downgrade to a lower subscri

Hello. I was wondering how I can find a list of all the shortcodes available in the membership plugin?

Also, if I have multiple subscription levels wherein level x is higher-priced and has more access to content than level x-1, is there a way to allow a subscriber to downgrade his/her subscription and get a refund? Thanks!