Apk download
v8.0.1 (1603)
v5.5.6 (1453) (The last version has Device admin mode)
Starting from v5.2.0, AppOps supports Sui. If your device is rooted, you can try Sui, it only requires you to install a Magisk module. (Select Shizuku mode)
Restore purchase from Google Play
To purchase or restore purchase from Google Play, you may have to install the app using adb.
adb install -i 'com.android.vending' <apk path>
This is because Google Play may refuse apps not installed from Google Play to initiate the purchase. The -i 'com.android.vending' in the command specifies the installer as Google Play.