To retrieve the parent item separately you can use the RecurringID property value of one of the instances as the ItemID parameter for the GetItemById call.
So, if i want to get a list of all futher events, i always get every instance of a recurrence? Even if the API offers an other mode?
I did a little bit of research in your sources and find out, that only one line of code need to be changed to make this switchable:
In the CloudCustomGCalendar - Unit in the "TAdvCustomGCalendar.GetCalendarInt" procedure
you only have to change the sinlgeevent - property in the API - Call to false. It wouldn't be a big deal to add a parameter or property to control this behavior.