I have an iPhone app (already in the App Store, free download) which requires the user to enter server and login credentials which are provided on a subscription basis. The app has a built-in 'Demo Mode' for prospective customers to evaluate the app, and so far the Apple app review team have always used this mode to approve each version submitted.
The latest version which I'm about to submit has some new features which are not appropriate for use in the Demo Mode and are disabled in this mode. No buttons are greyed out but an alert message is displayed to inform the user 'Not available in Demo Mode'. My question is will this cause a problem with the Apple review team - will it be rejected because of disabled functionality?
Yes, you should give out the subscribed user credentials in the review notes of the application metadata you fill in while uploading the application, as they need to test the full application to complete their review process. Until the full app is reviewed don't even think of it getting approved and going live.