iOS app downgrade compatibility requirements

Question

I was wondering if it's possible to downgrade an app from the app store (ARM binary) to a lower version. For example if the app requires iOS 5.0 or 4.3 or later getting it to run on iOS 4.2 or 4.0.

I understand that the requirements are important as the newer version contains API linked calls only exposed on the newer iOS platform. However, I've many apps that are cabable of running on lower versions are needlessly compiled on newer versions of xcode (just a minor update supports a huge jump on iOS supported version, like iOs 4.0 -> iOs 5.0)

What I would like to do is maybe downgrade an iOS 5.0 app to iOS 4.3 app by verifying that there are no new linked functions apis and thereby adjusting the plist files to the lower vesion? Can otool or class-dump help with this?

Answer 1

Yes, it's possible. Submit a binary with a different "iOS Deployment Target" (in Project > Info and Targets > Deployment Target), even if it is lower than the one you currently have.

You'll need to do extensive testing to make sure your code runs on the various compatible iOS, since a lot has changed with the release of iOS 5 (and subsequently, 6), meaning a lot of functions and methods will not be recognized in those iOS versions.

Regarding finding which API's may not work, here's a small discussion of [Finding unsupported API's with OS version][1]

[1]: finding unsupported apis with os version "Finding unsupported API's with OS version".