If you need to see the content behind a locked profile, you have three ethical options. None of them involve hacking.
A locked profile is a privacy setting that prevents non‑friends from: fb locked profile cover photo viewer
Even friends see a slightly limited view, but the main restriction applies to people not on the friend list. If you need to see the content behind
Most people cross-post content. If their Facebook is locked, check: Even friends see a slightly limited view, but
You might find the exact cover photo or tagged photos on these platforms.
Only if the profile owner chooses to share.