is there a running instance of my mobile application in the mobile device

Google is your friend. I googled "c# single app instance" and found this code. I don't know if it works, but it probably does:

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool SetForegroundWindow(IntPtr hWnd);

/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
    bool createdNew = true;
    using (Mutex mutex = new Mutex(true, "MyApplicationName", out createdNew))
    {
        if (createdNew)
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new MainForm());
        }
        else
        {
            Process current = Process.GetCurrentProcess();
            foreach (Process process in Process.GetProcessesByName(current.ProcessName))
            {
                if (process.Id != current.Id)
                {
                    SetForegroundWindow(process.MainWindowHandle);
                    break;
                }
            }
        }
    }
}

BTW, stop using "Plzzzzzzzzzz" in your messages. It just pisses everyone here off.