Your 1.7.13 cloud save is not lost, assuming you had an account and had it set to auto-save (as is the default). Beta is using a separate server with temporary new accounts: your 1.7 account isn't registered there. Your old cloud progress can be restored either later at official 1.8 release (or earlier if you opt out of beta on play store, uninstall, reopen play store again, reinstall, then reload cloud save after signing into your main account. Review https://infinitode.prineside.com/?m=open_beta_test for details (in the future, please read/understand such instructions before opting into beta beforehand).

Also there's a chance you have joined the Open Beta testers team a couple of years ago and agreed to receive Beta versions of the game - in this case Google Play may automatically update your game to Beta version.