You may be asked to complete "free" surveys or download unrelated apps to prove you aren't a robot, which generates revenue for the scammers while providing you with no actual data.
If you genuinely need to see someone's profile, there are only a few legitimate methods, though none of them involve a magic "free viewer" button: facebook private profile viewer free
It is a common curiosity. You stumble upon a profile on Facebook that piques your interest—perhaps an old friend, a potential date, or a hiring manager—only to find that their profile is locked tight. The content is restricted, and you are met with a generic silhouette and a "Add Friend" button. You may be asked to complete "free" surveys
No web form, browser extension, or desktop application can "force" Facebook’s server to hand over private data. The only ways to bypass this are: The content is restricted, and you are met