This will install a version of Facebook (likely version 26.0 or similar) that was designed to run on iOS 7. The Browser Alternative: Facebook Mobile Web
If the app version is too slow or crashes frequently—which is common on the iPhone 4’s limited RAM—the best experience is actually through Safari. Open Safari on your iPhone 4. Go to facebook.com. Log in to your account. facebook for iphone 4 ios 7.1.2 download
In the past, users turned to "Facebook Lite" or jailbreak tweaks like "Friendly." However, most third-party wrappers for iOS 7 have been discontinued. If the official app and the Safari method do not meet your needs, the device may be better suited as a dedicated music player or a secondary phone rather than a primary social media device. This will install a version of Facebook (likely version 26
A pop-up will appear saying: "Download an older version of this app? The current version requires iOS 13.4 or later, but you can download the last compatible version." Tap Download. Go to facebook