Attempting to bypass their privacy violates their trust and autonomy. If someone doesn’t want you to see their content, respecting that boundary is the mature choice.
If you share mutual friends, you may be able to see posts where they have interacted with your common connections, provided the audience is set to "Friends of Friends". Shared Groups: Attempting to bypass their privacy violates their trust
They make you fill out surveys to "unlock" the profile, which never happens. which never happens.