No. WhatsApp does not host old IPA files. Only the App Store’s legacy version serving is official.
: Devices locked at iOS 9.3.6, such as the iPhone 4S, cannot be updated to the required firmware versions to run the modern app. Apple Discussions 2. Alternative: WhatsApp Web whatsapp old version for ios 9.3.6 download
Even if you manage to sideload an older .ipa file, WhatsApp typically prevents these versions from connecting to its servers, displaying a "Version Too Old" error that mandates an update. such as the iPhone 4S