Since you won't use the Play Store, you must allow app installation from stored files.
: Uses cloud compression to render pages, making it much faster on slow hardware. Firefox Apk Android 4.2.2
While it is technically possible to install Firefox (specifically version 48.0) on Android 4.2.2, the user experience will be degraded, and the device will remain vulnerable to security threats. This configuration should be treated as legacy/maintenance mode only. Since you won't use the Play Store, you
Here’s a proper, balanced review of :
: Extremely small (under 2MB) and very fast on Jelly Bean. the user experience will be degraded
You absolutely need a semi-modern browser with privacy features on an ancient device and accept the security risks.