Last year I have developed an iPhone app that works well in iPhone 5 and 4 (iOS 7), it was compiled in sdk 7.
Now I am updating the app to compile it under sdk 8, in order the app works well in iOS 8. My question is: should I customize my app for iPhone 6 and iPhone 6 Plus?. I am afraid if I don't do it Apple could reject my app.
There are some great comments on this question.
How does an app with lower base sdk work?
"Apple never changes / deletes / renames classes or methods. They only add new ones. If they don't want you to use it anymore, they mark it as deprecated.
This is a very important point. At compile-time, the compiler checks if all classes and method signatures are available in the SDK your building your app with.
If that's the case, you can build and deploy your app. Because those classes and methods will never be deleted from newer versions of the framework, your app will run just fine."