You're going have to downgrade to 4.6.3 for Google Play to work properly. That's what I've read. Google how to do it. It is possible. I had the white screen on 4.6.3 but used the updated files in the first post and now it works. Downgrade then try this again.
How can I downgrade and ensure that it will not automatically upgrade as it has already done? Can you also post the files (or link to) that need to be installed, as there are so many different posts which make references to different files, I am so confused. Some of them are really old posts too, so not sure which runs are compatible with which versions.
Any reason not to root the phone and install Android (can this even be done?)? I am not crazy about the fire OS. There seem to be lots of simple basics just missing...