When you need information on using a specific Appian function that you have not used before, the first step should be to consult the Appian Documentation. The documentation provides comprehensive details on each function, including syntax, parameters, usage examples, and best practices, which is essential for understanding how to correctly employ the function in an expression.
References: Appian Documentation - Functions

When creating a new application in Appian and opting to generate groups and folders for organization and security, Appian automatically creates specific groups to facilitate application development and management.
The default groups include " Administrators " and " Designers " with the application prefix, in this case, ACM. The ACM Administrators group is intended for users who will have full control over the application, including configuration and deployment aspects. The ACM Designers group is designated for users primarily involved in the design and development of the application, granting them necessary permissions to create and modify application components without full administrative privileges.
References:
Appian Documentation on Application Design: Offers insights into best practices for structuring and securing Appian applications, including the use of groups for effective application management.

The union() function in Appian combines the elements of two or more arrays into a single array, removing any duplicate values. Given that the rule inputs ri!fruit and ri!vegetables are configured as text arrays, the expected output of union(ri!fruit, ri!vegetables) would be an array containing all unique items from both ri!fruit and ri!vegetables, with any duplicates removed. This function is useful for combining lists without repetition, ensuring a clean, unique set of elements.
Reference: Appian Documentation - Expression Functions

Based on the default behavior for task assignments in Appian, when a User Input Task is assigned to a group, any one member of the group can accept the task. Once accepted, the task becomes locked to that user, and they are responsible for completing it. This prevents multiple users from working on the same task simultaneously and ensures clear accountability.
References: Appian Documentation - Task Assignments and User Input Tasks