My app is available on the Appstore and is currently compatible with iOS 6 or later.
I want to release a new version only compatible with iOS 7 or later because there's a lot of crashes on iOS 6 with this new version and I have to release ASAP.
Here's my question : when the iOS 6 crashes will be fixed, would it be possible to bring back the iOS 6 compatiblity (i.e. downgrade the IPHONEOS_DEPLOYMENT_TARGET from 7.0 to 6.0) ? Does Apple allow that ?
Thanks in advance.
Your iOS Deployment Target can be whatever you wish it to be. The main requirement that Apple has is that your app submission is compiled against the latest SDK at the time (currently Apple is accepting base SDK of iOS 7, but it will change to iOS 8 in the new year).
When you downgrade the deployment target back down to 6, the only thing you have to ensure is that you're not calling any iOS 7+ APIs when running on iOS 6 devices, otherwise you'll be creating a lot of crash reports.
edited after better understanding the original question