If your device is running iOS 9.3.5, it might be worth considering updating to a newer iOS version. This will ensure you receive security updates and be able to download apps from the App Store.

Yes, Subway Surfers is compatible with newer iOS versions and can be downloaded from the App Store.

Because you are running a lighter, older version of the game, it won't overheat your legacy device or drain the battery excessively. The Challenge: Finding the "Best" Version The current version of Subway Surfers on the Apple App Store

You installed a version requiring iOS 10+. Fix: Delete the app, restart your device, and search for IPA versions labelled iOS 7 or iOS 8 compatible – these always work on 9.3.5.

You cannot just download an IPA and drag it into iTunes anymore (RIP iTunes 12.6.3).