Events

Yes. Events is available on every server, free plans included. The plan only sets how many events can be scheduled or live at once, as shown above.

It depends on the server's plan, as shown above. Only events that are scheduled or live count, so an event that has ended or was cancelled frees its slot. A recurring series does not count for its rule, but every occurrence that has been posted does.

No. Members sign up with the buttons on the Discord panel, and each member has a private ICS feed of the events they said Going to, which any calendar app can subscribe to. Connecting a Google account is optional, and can also let FlaviBot write those events into the member's Google Calendar.

The worker accepts /event create, /event edit and /event cancel from members with Manage Server, Manage Events or Administrator, and from holders of the manager role set in the module's settings. /event list, /event info and /event rsvp need no permission of their own. By default, though, Discord only shows /event to members with Manage Events, so an admin must open the command to everyone, or to the manager role, under Server Settings > Integrations. Members can always answer an event with the panel's buttons.