Need to register AzureAd app from Graph API and API permission for graph API for Application permission without Azure Portal

1. 1. I need to register the app from Graph API.
2. Add permission to an app, Microsoft Graph, and application permission.
3. Grant the application permissions.

All these three steps need to done from Graph API.

The first step is done below: Application gets created and we get the application id:

'16147e04-136b-4ea8-a45d-1cc2d9d0e0af'

string tenentId = "!!!!!!!!!-f8a6-4418-b062-26ad5b6608dd";
                string clientId = "!!!!!!!!-6beb-4a9c-bdc2-0092bc7feaae";
                string clientScret = "!!!!!!Huo3cUHtOOCHp1iNTSRQ7w9rDUlpRl6aqv";

          
                var accessTokenProvider = new BaseBearerTokenAuthenticationProvider(new TokenProvider());
                var graphServiceClient = new GraphServiceClient(accessTokenProvider);


               

                var requestBody = new Application
                {
                    DisplayName = "01N",
                    Description="This app is created from Graph API"
                };


                var result = await graphServiceClient.Applications.PostAsync(requestBody);

Problem: Not able to get this created app using below code:

        string clientScret = "!!!!!!Huo3cUHtOOCHp1iNTSRQ7w9rDUlpRl6aqv";
                // OnBehalfOfCredential onBehalfOf = new OnBehalfOfCredential(tenentId, clientId, clientScret, token);           

          
          

                var accessTokenProvider = new BaseBearerTokenAuthenticationProvider(new TokenProvider());
                var graphServiceClient = new GraphServiceClient(accessTokenProvider);

                // var result = await graphServiceClient.ServicePrincipals.GetAsync();

                var result = await graphServiceClient.ServicePrincipals.GetAsync((requestConfiguration) =>
                {
                    requestConfiguration.QueryParameters.Filter = "appId eq '16147e04-136b-4ea8-a45d-1cc2d9d0e0af'";


                    requestConfiguration.QueryParameters.Select = new string[] { "appId", "oauth2PermissionScopes" , "displayName", "appRoles" };
                    // requestConfiguration.QueryParameters.Select = new string[] { "id", "displayName", "appId", "appRoles", "oauth2PermissionScopes" };
                });

The response we are getting:

{
    "value": [],
    "additionalData": {
        "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#servicePrincipals(appId,oauth2PermissionScopes,displayName,appRoles)"
    },
    "backingStore": {
        "initializationCompleted": true,
        "returnOnlyChangedValues": false
    },
    "odataCount": null,
    "odataNextLink": null
}

Q1. How to add API permission inside created an application for Microsoft Graph: Application Permission?