iOS: Game Center show leaderboard with only my score ?

Hi, i'm making a leadearboard using with Game Center now, and i have 2 questions:

     static ILeaderboard m_Leaderboard;
     private int highScore = 1000;
     private string leaderboardName = "Test Ranking";
     private string leaderboardID = "55612367";
 //    private string achievementName = "70215624";
 
     // Use this for initialization
     void Start () {
         Social.localUser.Authenticate (ProcessAuthentication);
 
     }
     
     public void SendAndShow(){
         ReportScore(highScore, leaderboardID);
         DoLeaderboard();
     }
     ///////////////////////////////////////////////////
     // INITAL AUTHENTICATION (MUST BE DONE FIRST)
     ///////////////////////////////////////////////////
     
     // THIS FUNCTION GETS CALLED WHEN AUTHENTICATION COMPLETES
     // NOTE THAT IF THE OPERATION IS SUCCESSFUL Social.localUser WILL CONTAIN DATA FROM THE GAME CENTER SERVER
     void ProcessAuthentication (bool success) {
         if (success) {
             Debug.Log ("Authenticated, checking achievements");            
             Social.LoadScores(leaderboardName, scores => {
                 if (scores.Length > 0) {
                     // SHOW THE SCORES RECEIVED
                     Debug.Log ("Received " + scores.Length + " scores");
                     string myScores = "Leaderboard: \n";
                     foreach (IScore score in scores)
                         myScores += "\t" + score.userID + " " + score.formattedValue + " " + score.date + "\n";
                     Debug.Log (myScores);
                 }
                 else
                     Debug.Log ("No scores have been loaded.");
             });
         }
         else
             Debug.Log ("Failed to authenticate with Game Center.");
     }
     
     #region Game Center Integration
     ///////////////////////////////////////////////////
     // GAME CENTER LEADERBOARD INTEGRATION
     ///////////////////////////////////////////////////
     
     
     /// <summary>
     /// Reports the score to the leaderboards.
     /// </summary>
     /// <param name="score">Score.</param>
     /// <param name="leaderboardID">Leaderboard I.</param>
     void ReportScore (long score, string leaderboardID) {
         Debug.Log ("Reporting score " + score + " on leaderboard " + leaderboardID);
         Social.ReportScore (score, leaderboardID, success => {
             Debug.Log(success ? "Reported score to leaderboard successfully" : "Failed to report score");
         });
     }
     
     /// <summary>
     /// Get the leaderboard.
     /// </summary>
     void DoLeaderboard () {
         m_Leaderboard = Social.CreateLeaderboard();
         m_Leaderboard.id = leaderboardID;  // YOUR CUSTOM LEADERBOARD NAME
         m_Leaderboard.LoadScores(result => DidLoadLeaderboard(result));
     }
     
     /// <summary>
     /// RETURNS THE NUMBER OF LEADERBOARD SCORES THAT WERE RECEIVED BY THE APP
     /// </summary>
     /// <param name="result">If set to <c>true</c> result.</param>
     void DidLoadLeaderboard (bool result) {
         Debug.Log("Received " + m_Leaderboard.scores.Length + " scores");
         foreach (IScore score in m_Leaderboard.scores) {
             Debug.Log(score);
         }
         Social.ShowLeaderboardUI(); 
     }
     
     #endregion
 

• i get the Leaderboard ID in iTune is 55612367 (and the name of Leaderboard ID is "com.test.ranking"), and when i build and run app, it show "No score" or "No leadboard". But when i replace ID "55612367" to "com.test.ranking", it show leadboard with my score. Please explain me about it ?

• i use 2 account sandbox testers to test in 2 devices, but each device couldn't see each other's score. So how can i see other people's score in my leaderboard ?