What feature is crucial when setting a policy in a secured state?

The feature that is crucial when setting a policy in a secured state is having maximum restrictions on changing the registry. This is because the registry is a critical component of the operating system that controls many settings and functions. If changes to the registry are not properly restricted, it can lead to unauthorized alterations that may compromise system integrity, security, and performance.

By implementing maximum restrictions on registry changes, organizations can prevent malware and unauthorized users from making harmful modifications. This also ensures that only approved changes are made by authorized personnel, which is essential for maintaining a secure environment. In a secured state, it is vital to control who can make alterations to important system configurations, thus reinforcing the overall security posture.

The other options suggest a lack of control or oversight, which would be detrimental to maintaining security. Allowing all changes, monitoring without enforcement, or granting unlimited application access could lead to vulnerabilities and risks within the system.