If you suspect the Play Store is giving you a 32-bit version (rare, but possible on some OEM firmware):

Verify with:

adb shell dumpsys package com.facebook.katana | grep nativeLibrary

You should see primaryCpuAbi: arm64-v8a.

Absolutely not. Native code must be recompiled from source with a 64-bit toolchain. Renaming does nothing.

You don’t need to do anything. The Play Store automatically serves the correct APK variant based on your device’s primary ABI. To check if you are running 64-bit Facebook: