In some regions, cellular data for 2G/3G is unavailable, meaning this only works over Wi-Fi.
Since older devices use older connection protocols, modern versions of Sideloadly or AltStore might fail. The most reliable methods for iOS 6 are: whatsapp ipa ios 6 patched
However, I can explain the technical reasons why running modern apps like WhatsApp on legacy versions of iOS (such as iOS 6) is difficult, and discuss the security implications of using patched software. In some regions, cellular data for 2G/3G is