I tried to install Device Manager on my 7” tablet, but Play Store said it was not compatible with my device. It works fine on my 10” tablet, and I think it’s on the 11″ as well, so there was no logical reason it wouldn’t work on the 7”, especially since it has the same version of Android as the others. I downloaded APK Extractor onto the 10”, extracted the APK, transferred to the 7″,  allowed unknown sources (temporarily), and it installed just fine. Runs just fine, too. Liars.