A. Policies are refreshed every 90 minutes (5 on DC's). To force a machine to update the policy use the SECEDIT command.

To update the computer policy type

C:\> secedit /refreshpolicy machine_policy

To update the user policy type

C:\> secedit /refreshpolicy user_policy

Adding /enforce to any of the above forces a  reapply of the security policy even if there is no GPO change.