Is there any way for getting appstore id from running iOS application? (For asking user to rate it and providing link to appstore.)
You can use the Apple iTunes Link Maker to search for your App (or any app for that matter) and get your App Store URL. From there you could get your App URL which will remain the same for your App and put it in your Application. When you use itms:// instead of http://, it will directly open in the App Store app directly
For example, if I wanted to use the Twitter App URL, the link maker tells me the URL is:
http://itunes.apple.com/us/app/twitter/id333903271?mt=8&uo=4
Now do the itms trick:
itms://itunes.apple.com/us/app/twitter/id333903271?mt=8&uo=4
And it will directly open in the App Store than redirect via Safari then to the App Store,