Viewing a private Facebook profile picture in full resolution is restricted by Facebook’s privacy architecture. When a user "locks" their profile or sets photos to "Friends Only," non-friends are typically limited to a low-resolution thumbnail. Official Privacy Limitations
Viewing private Facebook profile pictures is not possible through official Facebook channels. While there are some unofficial methods that people claim can help, these methods may pose risks to your online security and personal data. The best approach is to respect people's online boundaries and ask them directly if you need to see their profile picture. view private facebook profile picture
Let’s start with the hard truth. The profile picture, however, exists in a unique gray area. Viewing a private Facebook profile picture in full