iOS - In App Purchase - auto renew subscription - How to get notified if the user cancel or auto renewable subscription?

I am working on an app which has our own user database and cross platforms subscription. and my questions are:

pre-condition: in iOS, user did login with username and did auto-renew subscription.

1.if user deleted the app, will it cancel the auto-renew subscription for the app?

2. if user cancel the subscription from settings or from itunes, how do we know which user canceled the services?(I dont have game center id). I would like to inform my server that this user canceled subscription.

basically, how do we know a user did auto-renew or canceled the subscription without opening app. Is there any unique id in apple's receipt which we can get to validate the user id.

Thanks.

Got a rough solution. Basically, when user subscribe from application, you should also send receipt to your own server, and then from own server use receipt to request from apple server for the status. This is for cross platform subscription. It is unnecessary for single platform app.