What is the format for referencing an entry in a page group property with index?

The correct format for referencing an entry in a page group property with an index is indeed by using the notation .PropertyName(1). This syntax allows you to access an individual item within a page group directly by specifying its index in parentheses.

In Pega, a page group property contains multiple instances of a page, and accessing a specific instance requires the use of an index, which is typically zero-based. However, the indexing in user interfaces is generally one-based, which is why you would use (1) to refer to the first entry. The dot before the property name indicates that you are referring to a property on the current page context.

Contextually, the other options do not follow the required syntax for accessing indexed properties. For instance, the use of symbols such as # or simply the property name without indexing fails to conform to the format that Pega recognizes for page groups. The reference without a dot is also invalid as it does not denote the proper context within Pega's page structure.