How to install GBwhatsapp?

It is not available for iPhone, probably because it is a hacked version of WhatsApp, and almost certainly defeats the end-to-end encryption that is the most important feature of WhatsApp and could also have other security vulnerabilities, spyware or back doors.

Yes, it is pretty easy to get a legitimate app into the iOS App Store (there are almost 2 million), so there is a real problem with any app that can’t pass Apple’s security and privacy requirements. Google’s Play Store is also pretty safe, but side loading apps on Android is pretty risky.