Whatsapp Backup and Restore with number change and phone change I needed to change my phone and mobile number both so this is how I proceeded:


I did an initial backup, which got saved both locally and on the G-Drive.
I used the Change Number feature to change my mobile number. Happened fine. Sent a couple of messages to check, and it was all okay.
I did another backup. This time, it only backed up locally, for some reason. My G-Drive was still connected though. Every time I clicked "Back Up", it would create a local backup and then just get back to the backup and restore screen as if nothing was amiss. Anyhow, I thought the local backup would be enough so I just continued.
I changed smartphones and loaded my sim into the new one(BTW, same google account used as the old phone). I downloaded whatsapp and opened it up till the phone number verification page. Then I connected my phone to a PC and replaced the Whatsapp folder in the internal storage with the Whatsapp folder from my previous phone.
I verified my number and it searched for my backup. It found the backup and asked to restore. I tapped Restore.
It started restoring messages and at some %(I did not note it at the time), it stopped and gave the following error message:


  Sorry, we were unable to restore any of your message history backups.

On clicking OK, it got to the Restore Backup page with no option but to click Next. (Under the Next button, "0 messages restored" was written)
My whatsapp did get activated and all(with my new number getting added to all groups and stuff), but with none of the previous messages.


Information: 

Old Smartphone- ASUS Zenfone 5 (Android 5.0)

New Smartphone- Samsung Galaxy Note 3 Neo (Android 5.1.1)

Old Number and New Number are from different countries, and currently because of my geographic location, old number cant be used

What all have I tried:

In the Database subfolder in the Whatsapp folder of my old phone, there are several msgstore-201X-XX-XX.1.db.crypt12 files, and in the Backups folder, one 'wallpaper.bkup' file.


I tried to rename the latest one (based on date written on file name) to msgstore.db.crypt, didn't work.
I created copies of the latest one and gave them different crypt extensions (msgstore.db.cryptZ, where Z is 8,9,10,11,12 and 13) to give the app all the options it may want. Didn't work. [This is the method I tried last, and I took a screenshot of the error message: http://pasteboard.co/iTeMJc92e.png ; I also noted that the restore process stops at 32%, after a pause at this percentage for a while]


Other info:


My whatsapp account has been through five smartphones and four mobile
numbers successfully, and contains a lot of messages precious to me. 
Also, another issue that has come up as a consequence of this is that
my verifications are getting limited (because after every failed
attempt, they make me wait till I can verify again, right now I need 
to wait 24 hours for my next "attempt")
The Old phone has been formatted, so the Internal Memory is changed now. However, I did copy the Whatsapp folder from it to my PC, and still have it.
I also e-mailed support@whatsapp.com, but they gave me a generic FAQ 
filled reply (to which I replied again, to which they have not yet responded). Their first reply did mention, however, that the verification process cannot be hurried up.


So, how do I fix this and restore my message backup? Please help!
Its a little complex solution but what you can do is start of the new phone and install the backup there while keeping the previously used number the same. Once you are done, insert the new sim and keep using it.

Number does matter, so before changing it, change the device.