Reschduing visa dropbox query

I have a Dropbox appointment on 20 July. due to some reason can’t attend the dropbox. I booked last year Sept 2022 and I already rescheduled 1 time.

  1. How many times i can reschedule the appointment?
  2. When I try to check the rescheduled date it was showing the OFC appointment. For Dropbox do I need to attend OFC /Biometric appointment?
  3. Is there any deadline that I have to attend the Dropbox appointment before the MRV fee expired?