Navigate to the WhatsApp application directory: /var/containers/Bundle/Application/WhatsApp/WhatsApp.app/ (or similar path depending on iOS version). Locate the Info.plist file and open it.
Attempts to jailbreak or install unsupported apps can brick an older device.
Most older versions of WhatsApp are hard-coded to expire after a certain date.
Even if you managed to find an old .ipa file (the iPhone app format), the application would fail to connect to WhatsApp's servers because they now require modern security protocols that iOS 7.1.2 cannot support. Current Status for Older Devices
While official channels are closed, some users attempt the following: WhatsApp On IOS 7.1.2: What You Need To Know - Ftp
Downloading and using an old version of WhatsApp on iOS 7.1.2
Note: Modern sideloading tools rarely support iOS 7. You may need a PC running macOS Mojave or Windows 7 with iTunes 12.6.x.
If you are holding onto a classic Apple device—an iPhone 4, iPhone 4s, or the original iPad—you are likely stuck in a frustrating limbo. These devices are permanently locked to (or iOS 6.1.3, with 7.1.2 being the final update for the iPhone 4).
Usually not. Hackers embed tracking profiles in modified IPA files. Only use hashed copies from known archive teams.
: Tools like Pangu are historically used for iOS 7.1.2 jailbreaks.
That is a phishing trap.