Because you cannot use the Play Store, you must install the APK manually:
Because you cannot use the official Google Play Store for this process, you must perform a manual installation, also known as "sideloading." Step 1: Enable Unknown Sources
If you own a device running Android 4.1.2, you have likely encountered a frustrating problem: the official Facebook app from the Google Play Store is no longer compatible. When you search for "Facebook," you either see an error message saying "Your device isn't compatible with this version" or the app fails to install.
You will not have access to modern features like Stories, Reactions, Reels, or Live Video.
Similarly, the main Facebook app may not have built-in messaging, requiring a separate older version of Facebook Messenger.
Fast loading times, low storage footprint, works on 2G/3G networks. Option B: Legacy Standard Facebook App
Before installing any APK, you must allow your device to install files from outside the Google Play Store: Go to > Security (or Applications on some models). Find "Unknown Sources" and check the box to enable it .
Check the minimum system requirements listed on the download page to ensure it explicitly states compatibility with (Jelly Bean).
Elias knew the Google Play Store was a dead end. It offered him nothing but a "Your device isn't compatible with this version" message. He needed a time machine.