In the past, Firefox was available on Android devices running on a variety of versions, including 4.2.2. However, as Android and Firefox continued to evolve, compatibility issues and security concerns led to the discontinuation of support for older versions of Android.
If your device is extremely low on RAM, an older legacy version like 42.0.2 might perform faster, though it will lack modern web standards and security. These are available at OldVersion . How to Install the APK Firefox Apk Android 4.2.2