Hi
On the backend, I need:
- custom fields on the event registration form

RSVP Pro offers sophisticated registration form templates that you can create with your own custom fields.

- update a registrants reservation on an event (paid/unpaid, waiting, canceled)

You can edit and update registrations (e.g. adding manual payments, cancelling etc.) BUT the waiting list is automatically handles - the earliest member of the waiting list is always the one who is 'promoted' when space becomes available.

- a list of all registrants for a specific event

Standard feature of RSVP Pro - you can export this list as a CSV file including all the custom field data

- the possibility to e-mail this list + custom fields to the registrants

You can send emails to all the attendees of an event or a selected subset.

- a list of registrants who did not pay for their reservations (off line payments) + possibility to e-mail a reminder

See the previous point - note there is not automated reminder to make a payment but that is a good idea which I will look into.

- only registered users can subscribe for an event - is JEvents integrated with Joomla Profile?

You can configure this so that attendees MUST be logged in before registering for an event

- a checkbox to indicate if the registrant was present on the event

There is a 'did attend' checkbox - I am part way through implementing a barcode/QR code integration for this so that a printed ticket can be scanned at the venue to confirm actual attendance

- a list of all the events that a member subscribed for.

The visitor can see a list of all the events they have subscribed for.

These features are part of RSVP Pro which is a gold member addon.

Thank you, Geraint.
I will propose Gold memebership to my client and hope to place my order soon.
Kind regards,
Peter