Yes, it's very possible to operate two WhatsApp account on the same phone if you are using different phone numbers and different WhatsApp App.
You can decide to use two different phone numbers when you have two different WhatsApp App: both GB WhatsApp and the normal WhatsApp.
Note that you can't use the same phone number on both WhatsApp, cos it won't work out at all. Even if you did use the same phone number on different WhatsApp, it would be required of you to verify your phone everytime you tried to open your WhatsApp App (at every time intervals, your WhatsApp account will fluctuate, asking you to re-verifies your phone number again)
Image source: blog.parallelspace-app.com
It is possible to run two Whatsapp messaging apps on a device that runs Android OS. I don't know much about devices that run IOS. The second Whatsapp app can be cloned using an app called Parallel Space. It would have to be downloaded from Google Play store or trusted android apps website, launch the app, and simply select the app you would want to clone.
Yes very possible