Forms is a Microsoft 365 Tier-D service and part of the Microsoft 365 compliance program. More information about Microsoft 365 compliance is available at the Microsoft Trust Center.
Yes, by assigning licenses to users, you control whom in your organization can access Forms.
External sharing is available for GCC environments, but disabled for GCC High environments. Learn more.
Customers can learn more at https://support.office.com/en-us/forms.