Which of the following cannot be configured through a Catalog UI Policy?

The correct response indicates that applying a requirement to all form views cannot be configured through a Catalog UI Policy. Catalog UI Policies are primarily designed for controlling the behavior of variables on Service Catalog items in specific scenarios. While they can set variables to mandatory or read-only and can also manage reverse UI policies based on certain conditions, their scope is limited to individual catalog items or forms.

When it comes to applying a requirement universally across all form views, this falls outside the configuration capabilities of a Catalog UI Policy. Typically, such requirements would need to be implemented through other means, such as business rules or global script includes, which can affect more than just the UI Policy's designated catalog item.

The other options, such as setting a variable to mandatory, reverse UI policies based on conditions being false, and setting a variable to read-only, are all functionalities that can be effectively configured within the context of a Catalog UI Policy. These functionalities are integral to customizing user interactions with service catalog items on a per-item basis.