In group reporting, the currency translation method is assigned to the consolidation unit (B).

In SAP Group Reporting Data Collection forms, the possible period mode is Periodic, which represents monthly, quarterly, or yearly periods.

The update schedule for SAP Group Reporting Data Collection is once a month. This ensures that the data used for group reporting purposes is up-to-date and accurate.

In SAP S/4HANA Finance for Group Reporting, group journal entries can have attachments such as Excel files, URLs, and Word documents. These attachments can provide additional information and context to the journal entry, making it the underlying transactions (SAP Help Portal: Group Journal Entries)

According to the SAP S/4HANA Finance for Group Reporting Associates documents1, group journal validation and substitution have the following things in common:
Preconditions: Conditions that define when a validation or substitution rule is executed. Preconditions can be based on different dimensions or attributes of the data, such as company code, account type, etc.
Filtering logic: Logic that defines how data is filtered and selected for validation or substitution purposes. Filtering logic can be based on different operators or expressions, such as equal to, greater than, contains, etc.