In my iphone app, I used some API new in iOS 5. Since I don’t have code to check iOS version and provide fallback for old iOS versions, this app is obviously not going to run on any iOS older than 5.0.
Will the app be rejected because of this? Or can I specify that my app requires iOS 5 or later, upon submission to app store?
You should specify your minimum OS version in your Info.plist. To set it in Xcode, click on your project, select the ‘Summary’ tab and put 5.0 in the ‘Deployment Target’ field.
If you were to upload an app with a deployment target of 4.0, and your app were to crash on 4.0 due to attempting to use unimplemented API then that would be grounds for rejection.