What are the signs your (stolen) phone has been wiped/hard reset?
No, as the device will require the new password before it will successfully log in to the Play Store app to download any apps.
Again, No as it will not send any data to Google because you've changed your password.
I'm not aware of any way to find out this information. Unfortunately by changing your password and ending sessions there is no way to communicate with the device using your Google account.