Is it technically possible?

Older YouTube tutorials suggest: Right-click > Inspect > Find the cover photo URL in the div class.

This worked briefly in 2018–2019 when Facebook lazy-loaded images without checking friend status on the CDN level. Today, Facebook serves images via time-limited, user-specific tokens. Even if you extract the URL, opening it in a new tab returns a permission denied error or a generic gray placeholder.

The image simply does not exist on the server for your session.

If you encounter a site offering an "FB locked profile cover photo viewer top," consider these dangers:

Most such tools ask you to "Login with Facebook" to use the viewer. This is a classic OAuth phishing scam. Once you enter credentials, your account is compromised.