Apple let's you download older versions of apps/games if the newest version isn't compatible with the device.
Apple only allows it when the app developer goes to extra effort to make that possible. Here is the Apple page describing this: http://support.apple.../en-us/HT201377
Find the app and choose Download. You'll see a message telling you if a compatible version is available. Tap Confirm to install this version.
If a compatible version isn't available, you can try contacting the app developer. Look for contact information on the app's product page in the App Store or Mac App Store.
For most apps, once the app requires iOS 7, there is no way to download the iOS 6 version of the app, without updating your device to iOS 7 first.
But if the Ari wants to, and if Apple will allow it, Eden 1.7 can be made available. Remember that Apple shut down Eden 1.7 for a while, and Ari was only allowed to put it back on the app store by disabling search. So we might end up with an Eden 1.7 that has no search, for use by people like me who still have iOS 5.0
The app developer could also choose to create another separate version of the app, called "MegaGame Classic", to run on older devices, or they can leave "MegaGame" alone and make the new app called "MegaGame Pro".