How to find out the OpenGraph id (and eventually get the list of posts from the page)?

Question

Facebook

I'm having trouble getting the object id via OpenGraph
I'm using Koala for Ruby, but I guess it's the course of action that matters, not the library
What I'm doing
1) Get an app access token

oauth = Koala::Facebook::OAuth.new
token = oauth.get_app_access_token
fb    = Koala::Facebook::API.new(token)

Everything works fine
. Then the incomprehensible begins. I'm trying to get the OpenGraph id of an object in order to get the post feed from the page. And so I take, for example, https://www.facebook.com/karcher.russia Everything is fine, I get the response json But, for example, for the page https://www.facebook.com/Alfred.repair/ - it also seems to be businesslike page I receive
fb.get_object('karcher.russia')
fb.get_object('Alfred.repair')

Koala::Facebook::ClientError: type: GraphMethodException, code: 100, message: Unsupported get request. Object with ID 'Alfred.repair' does not exist, cannot be loaded due to missing permissions, or does not support this operation. Please read the Graph API documentation at https://developers.facebook.com/docs/graph-api, x-fb-trace-id: CRtsR63zUd2 [HTTP 400]

Further, according to the plan, I wanted to call fb.get_connection(id, 'feed', {}), and where it turned out to find out the id - all the rules.
Through Facebook Graph Explorer everything works with my personal token, but not with the application token. Maybe it's in the application settings?
What is the difference?
How to legally get an OpenGraph id?
Or is it not necessary to get a list of posts from the page?