I want to access notes and calendar using native iphone app. I want to know is it possible in new iphone os? Is there any public pi for that?
There is the Event Kit API which is documented in The Event Kit Programming Guide.
As far as I know you cannot access Notes.
The Event Kit and Event Kit UI frameworks together allow iOS applications to access event information from a user’s Calendar database. You can fetch events based on a date range or a unique identifier, receive notifications when event records change, and allow users to create and edit events for any of their calendars. Changes made to events in a user’s Calendar database with Event Kit are automatically synced with the appropriate calendar (CalDAV, Exchange, and so on). This document describes Event Kit concepts and common programming tasks.