Api, Sdk Facebook - get information without login

No it can not be done. In fact, it has never been possible.

In the past (until before the Cambridge analytics scandal ) if you were logged into Facebook you could search for your "friends" by phone or email. This led unscrupulous companies to acquire databases of millions of emails and telephone numbers, and through a scraper they associated them with facebook profiles, and with this crossing of bases they also used them for unethical purposes.

After the scandal, Facebook no longer allowed to do this as a user, logged into the platform and via the web. However, through the API it was never possible , not even before the scandal.

It seems to me that today, if anything

1. your application had a login,
2. a user will log in and grant you the permissions pages_adminand pages_show_list,
3. your application also had the approval of Facebook (prior application for review) to request such permissions
4. the user had the role of admin or moderator of the page

Then you could hit the endpoint feedof this one, and through that you would get the posts, and from the posts you would get the comments and reactions, and from these you would get the user_id. However, these are user_idspecifically related to that page. The same person has another user_idwhen interacting with another page, just so you can't combine those ids with your own databases.