Lin
Thanks for reaching out, Here what you can do to block. Google play uses following network block:
216.58.192.0/19
195.8.0.0/19
you can create custom url and tie with the policy using this IP block, As for the blocking during working hours.. you can configure Time base ACL and tie with the policy as well.. (online help or user guide provide details steps).
Please make sure to "nslookup play.google.com" from your WSA CLI to to get the ip block from your region for play.google.com.
Pleas let me/us know if you have ANY questions,
Regards,
Zack