Use the original version of the app, not a cloned one or reinstall Google Play Services if you uninstalled it. These are the only two known reasons why this happens.
A friend of mine had same problem What device are you using? He was using blackberry's droid phone Also I have heard this happens with people using a certain app that lets you have multiple accounts for a same game
Yes, This is correct. The game can be modified though by using an APK Editor. Of course no of of will save but error can form due to mistakes made will attempting to decompile and modify the game. Edit: If using a Kindle or Amazon device, make sure it's registered. I had the same issue when I didn't activate my device.