I would like to know if it is possible to sync between the Reminders app and the Calendar app.
Or it will be nice to be a new Reminders App feature :)
Thanks
Reminders connected to Calendar
If I understand your question, you want a way to link a calendar event and reminder together? That functionality doesn't currently exist in EventKit but you could store enough information in your own database in order to maintain a mapping between calendar events and reminders.
The best place to submit feature requests for first party apps is https://www.apple.com/feedback/.