Since today the answer is not quite correct. If someone didn't use this: AppEventsLogger.activateApp(this);

Since last update you must do it or your app will crashed. And you also should pass Application here not Context

https://developers.facebook.com/docs/android/getting-started

// Add this to the header of your file:
import com.facebook.FacebookSdk;

public class MyApplication extends Application {
    // Updated your class body:
    @Override
    public void onCreate() {
        super.onCreate();
        // Initialize the SDK before executing any other operations,
        FacebookSdk.sdkInitialize(getApplicationContext());
        AppEventsLogger.activateApp(this);
    }
}

Initially I was getting only id and email in JSONObject object of onCompleted. Even though I set permissions like "public_profile" and "email" which is sufficient enough to get the id, name, email and profile picture from facebook. But somewhere I went wrong and didn't understand and added Profile and did getProfile() so I can get the name and profile picture. Then other problem arised was even after login perfectly, I was getting null profile sometimes(may be once in 5 times). For that had to put Profile Tracker and this was because Profile works Asynchronously(was too confusing for me as you have to put trackers and start & stop tracking).

Then I realized where I went wrong. In the bundle where we need to mention what all we want in the json object as reply, I had only mentioned "id". So now in the below code I added "name" and "email" as well. So in the JSONObject object response I get the name and email as well.

And for profile picture I saw How can I display the users profile pic using the facebook graph api? and implemented this using Uri builder Use URI builder in Android or create URL with variables . So with this I removed the use of Profile completely and still getting all the data I wanted.

This answer is the mixture of both the answers mentioned by Destro - Android Facebook Login- Profile is null & How to get email id From Android Facebook SDK 4.6.0?

FacebookCallback<LoginResult> facebookCallback = new FacebookCallback<LoginResult>() {

        @Override
        public void onSuccess(final LoginResult loginResult) {


            GraphRequest request = GraphRequest.newMeRequest(
                    loginResult.getAccessToken(),
                    new GraphRequest.GraphJSONObjectCallback() {
                        @Override
                        public void onCompleted(JSONObject object, GraphResponse response) {

                            if (BuildConfig.DEBUG) {
                                FacebookSdk.setIsDebugEnabled(true);
                                FacebookSdk.addLoggingBehavior(LoggingBehavior.INCLUDE_ACCESS_TOKENS);


                                String uid = object.optString("id");
                                String email = object.optString("email");
                                String name = object.optString("name");

                                Uri.Builder builder = new Uri.Builder();
                                builder.scheme("https")
                                        .authority("graph.facebook.com")
                                        .appendPath(uid)
                                        .appendPath("picture")
                                        .appendQueryParameter("width", "1000")
                                        .appendQueryParameter("height", "1000");

                                Uri pictureUri = builder.build();

                                try {
                                    sendLogin(uid, name, email, pictureUri.toString(), "fb");
                                } catch (JSONException e) {
                                    e.printStackTrace();
                                } catch (IOException e) {
                                    e.printStackTrace();
                                }
                                facebookLogout();

                            }
                        }
                    });
            Bundle parameters = new Bundle();
            parameters.putString("fields", "id, name, email");
                    request.setParameters(parameters);
            request.executeAsync();
        }

        @Override
        public void onCancel() {
        }

        @Override
        public void onError(FacebookException e) {
            Toast.makeText(getApplication(), "Something went wrong, please try again later", Toast.LENGTH_LONG).show();
        }
    };

    public void facebookLogout() {
        LoginManager.getInstance().logOut();
    }