Which option is NOT a valid method for configuration backup restoration on Firebox?

The answer points to the notion that using the Upgrade OS feature in Fireware is not a valid method for restoring a configuration backup. This is because the Upgrade OS feature is intended solely for upgrading the operating system of the Firebox device and does not serve the purpose of restoring any configuration settings or backups.

Restoring configurations typically involves methods that directly interact with the saved configuration files or previous system states, rather than merely upgrading the system software. For example, using an archived image from a previous version implies accessing and applying a saved configuration that aligns with what is required for a proper restoration. Likewise, the downgrade feature in the Policy Manager is specifically designed for reverting to an earlier policy configuration, ensuring that the desired settings can be restored effectively. Manually restoring configurations through the Web UI is also a recognized method, facilitating direct user interactions to revert to previous settings.

In summary, while the Upgrade OS feature performs a critical function in maintaining the system's software, it does not specifically address the task of restoring configuration backups, which is why it is identified as the incorrect method in this context.