App Store: Install the latest compatible version of an app
iOS 7 and OS X Mavericks include new features that many of your favorite apps take advantage of when you update them. Some of these features are specific to the latest versions of iOS and OS X. As a result, the latest versions of some apps may not work with your device or computer if you are still using an earlier version of iOS or OS X. Thanks to the App Store, you may still be able to re-download a compatible, earlier version of an app when you are using an older operating system.
Managing Availability of Your Apps' Previous Versions
Previous versions of your apps are now available for re‑download by users who have already purchased them, allowing customers to use your apps with older devices which may no longer be supported by the current version of your app. If you do not wish to make these versions available, you can manage the availability of your apps' previous versions in the Rights and Pricing section of the Manage Your Apps module in iTunes Connect.