So the story could end with them realizing they need to upgrade their phone, or find an alternative way. Or successfully getting a verified APK with the friend's help, highlighting the right steps to follow.
Try to register your phone number. If it says "Your version is outdated," you may be forced to try a slightly newer (but still old) APK, or the device may no longer be supported. Alternatives for Old Android Devices whatsapp apk para android 412 verified