I have used the Validate tool in xcode and validated my application. The validation was OK and it says i could submit my app to appstore.
I need to know if the Validate process in xcode successful, does it mean my app is free from Private APIs and etc, and has 0 possibilities to get rejected when i submit my app to appstore for approval ?
Note: I am using xCode 4.2
No it does not mean that at all. It mostly means that it was signed correctly. The only way to know that is to submit it, and wait for a response.
Also note: Your app could still be rejected for many reasons, not just for private API calls.