Meta API Access Guidance

My Facebook-based project needs to tap into Meta-supported APIs that handle user authentication, yet the specific endpoints and resources keep showing as “missing or unavailable.” I need a clear, practical walkthrough that gets me past these roadblocks and leaves me confident in the overall technology stack.

Here’s what I need you to cover:
• Explain why the authentication-related items fail to appear in my developer account and how to enable or request them correctly.
• Walk through the entire setup flow—app creation, required permissions, token generation, and any App Review steps—so the APIs become accessible.
• Provide a concise, runnable code example that authenticates a test user (language of your choice, but make sure I can reproduce the result).
• Document each step so I have a reference for future Facebook projects.

I’ll supply current app details and any error screenshots once we start. The job is complete when I can successfully call the user-authentication endpoint from my environment without the “unavailable” notices and understand why it works.