Re: Old iPhones ?
"So developers can not produce apps for the old iphones or ipads (iphone 5 and earlier can not run ios 11)."
Please don't talk about things that you don't now anything about.
As an iOS developer, you pick the SDK - that determines what features you can use. If you use the iOS 10 SDK, then you can't use iOS 11 features. So Apple tells you your app must be able to use iOS 11 features.
The other choice you make is the "deployment target", which is the lowest iOS version on which your app will run. If you use iOS 11 SDK + iOS 9 deployment target then your app runs on an iOS 9 device, can use all the iOS 9 features, can use iOS 10 features when running on iOS 10, and can use iOS 11 features when running on iOS 11.
Since every iOS device that can run iOS 8 can also run iOS 9, iOS 9 is a good choice for the deployment target. (Anyone running iOS 8 couldn't be bothered updating their device, so they are not going to bother buying your app. Anyone running iOS 7 has an iPhone 4 or older, not even an iPhone 4s, so they are not going to buy your app either. )
Biting the hand that feeds IT
