What do you define as "automated email campaigns"? Drip campaigns? If so, the software does not build drip campaigns. We do have an automated notification system which notifies users of activity they have opted-into though. Our software also allows for manual email campaigns to be sent out users.
Commerce can facilitate free trials and items at no cost, if that answers your question.
Yes, Stripe is a payment method in Commerce.
This is not part of the software. With that said, we do have the ability to "agree" to your Terms of Service and Guidelines. If you make a change to these items, users are required to re-attest their agreement.
Yes, the Events system can be used to announce/give details about in-person meetings/events.
It is not a CRM system but depending on your needs, it may fill some needs there as members/customers would be stored in the system with their contact information or any fields you require. However, there are no elaborate CRM features.
Invision Community has elaborate permissions and logging for your staff administrators and moderators. However, I am not quite sure what you're looking for here. If you can elaborate on the need, we may be able to provide more information.
Unfortunately, there is no simple answer to this. What/how you program integrations would detail exactly the answer to that. I can say that we have a major new release coming out relatively soon in version 5. This is a new approach to allowing third party customizations to our software so would require any applications/plugins developed for version 4 to be re-done.
With that said, on minor releases, the upgrades would depend on what has changed in the software and how your application/plugin integrates with that.