
Explanation
Box 1: 4
The infrastructure of the integrated system must be backed up as frequently as possible.
Enable backup for Azure Stack Hub from the administrator portal
The frequency in hours determines how often backups are created. The default value is 12. Scheduler supports a maximum of 12 and a minimum of 4.
Box 2: Azure key vault
The integrated system backups must be retained for 28 days.
Online retention policy. This specifies the time period during which daily, weekly, monthly, and yearly backups are retained in the Azure Site Recovery vault that's associated with the local MABS instance.
Reference:
https://learn.microsoft.com/en-us/azure-stack/operator/azure-stack-backup-enable-backup-console
https://learn.microsoft.com/en-us/azure/architecture/hybrid/azure-stack-backup