1. there are separate buttons for deleting a specific event and deleting all recurrences. I will log a request for an option to only delete future recurrences. for now it could be done by deleting the individual future events.
2. that is a tall order. creating the recurrences is a challenging thing to implement so that it works correctly spanning time zone changes from daylight savings to non-daylight savings etc. individual event records are created for each recurrence so changing it after the fact would introduce significant complications. if it were easy to implement I would do it but for now I suggest plan carefully when creating recurrences and if you need to change it you'll have to delete it and then re-create it. I will log this request but can't promise a solution.