Facebook API Lead retrieval for internal business app should i submit for App Review

I am building a dedicated CRM solution and it is supposed to show the list of Facebook leads of the client and then convert manually it to internal lead . I am managed to setup a websocket client and Facebook is sending me lead details including leadgen_id.

{
"object": 
"page" ,
"entry": [{
"id": "*****" ,
"time": 1627211279 ,
"changes": [{
"value": {
  "form_id": "******" ,
  "leadgen_id": "******" ,
  "created_time": 1627211277 ,
  "page_id": "******"} ,
 "field": "leadgen"}
]}
]} 

Then i have created an user access_token using Facebook's graph api and requested for the details of the leadgen_id using api endpoint

 https://graph.facebook.com/v11.0/<LEADGEN_ID>?access_token=<ACCESS_TOKEN>

I was able to get the details of the test lead I created with the Facebook 's lead testing tool. But when accessing the production leadgen_id I am getting an exception with following as response.

{
    "error": {
        "message": "Unsupported get request. Object with ID '<LEADGEN_ID' 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",
        "type": "GraphMethodException",
        "code": 100,
        "error_subcode": 33,
        "fbtrace_id": "*********"
    }
}

Then I have tried using a system user token and its not even working for the test leads. In some part of documentation it is saying that I need to complete App review to access live data using lead_retrieval and in some other part of documentation its quoted that I don't need app review to use API for internal users . And I don't get the point of creating a 'login with Facebook' for this internal app specific for one user . Is there anyway other way than completing app review to access lead details using leadgen_id ?

Its turns out I need to complete the app review specifying it as a 'Server to server app' on the review description, which doesn't need any Login with facebook button . Got the idea from https://developers.facebook.com/docs/app-review/resources/sample-submissions/server-to-server/