Linda,
Thanks for getting in touch. Unfortunately we don’t support random recurrence, as there’s no pattern to use if it’s random. 🙂 You can have events that recur daily, weekly, monthly, or yearly. We also have the ability for custom recurrence (screenshot).
Yes! The upgrade process is seamless and all of your events are left in-tact. You’ll need to make sure that you’re already running the latest version of The Events Calendar prior to installing the PRO add-on, but other than that, it’s pretty seamless.
Hopefully that helps to answer your questions. Thanks! 🙂
-Casey-