Hamed!,
Please, don't be angry with me!,I just wanted to tell you my opinion about that.
Of course, I read your article carefully. Your four steps are awesome!, I have no doubt about that!,
If I told you something bad, I really apologize.
About the doubts I had:
1) Video calls: yesterday night, I checked whatsApp FAQ's in his website. Sadly, video Call is NOT supported for BB10 any longer. It's only available for Android OS (4.1+), iOS (8.0+) and Windows Phone (8.1+):
https://www.whatsapp.com/faq/en/general/26000025
After read that, I've tested video calls on iOS (Apple iPhone 5c), Android (Motorola Moto E) and Windows Phone (Nokia Lumia 640 XL) and they worked very well!
2) WhatsApp directory: I had understood that when we moved the WhatsApp directory from the device to the MicroSD, it was not going to appear again in the device.
Maybe I was wrong, but it was just only a doubt I had about that.
3) WhatsApp version: the link you said es from the original WhatsApp website, it's alright, but, it isn't the latest version. This version is the 2.17.188 and apkmirror version is the 2.17.190.
Believe me, apkmirror get the original source from the google servers (I read his entire FAQs) !
Tomorrow, I will do this four steps in other BlackBerry Z30!. A friend asked me to help him with the process. I'll tell you later!.
I hope that my tests was helpful for all!,
Regards from Buenos Aires, Argentina!