I have requirements for the iOS app. Devices that must be supported and iOS versions are listed by the customer.
It is written that the app must support: - devices: from iPhone 4 and above; - iOS versions: 7, 8.
I feel myself misled. As far as I know iPhone 4 is not in the iOS 8 supported devices list. That's why I have to target to the iOS 7.1.2 - the one that currently supported on all required devices.
How can use benefits of the iOS 8 in this app? Could you help me with good references that will help me to understand the intricacies of this question?
In short:
Yes, you can but not on the device running with the older version of a system (so you will need conditions for such cases).
Detailed explanation:
If your app has to be compatible with iOS 7 then you can not use iOS 8 features on the system which is older. This is quite obvious, system can not understand commands that haven't been implemented yet. Although you can use in your app API that was revealed in iOS 8 but you have to create, at least, conditions checking agains which system version you run if you want to avoid troubles like app crashes. Quite a good reading for better understanding an issue can be this article. Here you have quite a nice graphic presenting which device supports which version of a system (according to your question about iPhone 4).