Recommendation: If you must use it, never click on unknown links and assume your chat history is not secure.
Warning: This is not recommended. It involves security risks and manual updates every few weeks.
If you absolutely must try to use WhatsApp on this specific device because you have no other option, you must bypass the Google Play Store:
Why this will likely fail: Even if you install the latest APK, the app performs a server-side check. When the server detects you are connecting from a device running Android 4.4.2, it will eventually block the connection for security reasons. You will see a message saying: "WhatsApp works with Android 5.0+ and above. Please update your device."
Fix: The app is trying to reach an API endpoint that uses TLS 1.3. Android 4.4.2 only supports TLS 1.0/1.1. You need to root your phone and install a library called "TLS 1.2 Patcher" – an advanced hack.