When an occurrence of a recurrent appointment is deleted, AppointmentEditing and AppointmentEdited events of the ScheduleView are fired. In AppointmentEditing event handler the second argument which is of type AppointmentEditingEventArgs
has IsDeleted property - it is true when the occurrence is deleted, false when the occurrence is edited. More information about RadScheduleView events can be found here
As to the second question - the method returns false in cases when the parameter is not of type IAppointment or Occurrence, also when you try to delete an appointment which is at the same time in edit mode.
Hope this helps. If you have any additional issues/questions, please let us know.
the Telerik team