I have structured this to be user-friendly, explaining how to find the file, which version you need, and the risks involved.

: WhatsApp uses a server-side check. If the server sees your app version is too old, it will force a disconnect. Unfortunately, there is no permanent software workaround for this server-side "kill switch." Safety and Security Risks

Whatsapp For Kitkat 4.4 2 Download Old Version