Architecture: iOS 7.1.2 was a bridge between 32-bit and 64-bit eras. While the iPhone 5s supported 64-bit apps, the iPhone 4 and 4S are strictly 32-bit. You must ensure the IPA file you find contains the "armv7" slice.
When working with IPA files, be aware of the following risks:
For iOS 7.1.2, you are limited to older versions of apps that still support 32-bit architecture. Finding these files can be difficult because the App Store often only offers the newest version. 1.2 and how to develop/install them. Where to Find IPA Files for iOS 7.1.2
An IPA file (iOS App Store Package) is a file format used to distribute and install iOS applications on Apple devices, such as iPhones, iPads, and iPod touches. IPA files contain the app's binary code, resources, and metadata, and are essentially a zip archive with a specific structure.