Older versions lack patches for critical remote code execution (RCE) flaws, leaving your phone exposed to targeted exploits.
If you install an old version and see a "This version of WhatsApp became out of date" message, you can try these workarounds:
This method tricks the application's internal check by altering the device's system time. Put your phone into and turn off Wi-Fi. Go to Settings > System > Date & Time . Turn off Set time automatically .