An IPA (iOS App Store Package) is the application archive for iOS. It’s essentially a ZIP file containing executable code, images, and metadata. For older devices, you need an IPA that was compiled with an SDK supporting ARMv6 or ARMv7 architecture (which iOS 5.1.1 uses).
You can find original .ipa files on The Internet Archive , which hosts historical versions like 1.0 or 1.10.2.
One of the most reliable places for "Whitelisted" apps that work on older firmware.
If you cannot get the IPA to work, here are excellent alternatives that run natively on iOS 5.1.1 and offer similar endless running mechanics:
