How to get the BLE device where I have connected in android 4.3?

Question

I am developing an application where I have to connect to Bluetooth device on Android 4.3.

I can scan and connect to the device, and I want to connect to multiple BLE device and list them.

I have find the getConnectedDevices(), but it has multiple type in BluetoothHeadset , BluetoothProfile and BluetoothA2dp.

**First question is **What the different between there three API ??? Which is better ??****

I have try the code of the following:

public class Main extends Activity {
    private BluetoothHeadset mBluetoothHeadset;
    private BluetoothAdapter mBluetoothAdapter;


    private BluetoothProfile.ServiceListener mProListener = new BluetoothProfile.ServiceListener() {

        @Override
        public void onServiceDisconnected(int profile) {
            // TODO Auto-generated method stub
            if(profile == BluetoothProfile.HEADSET) {
                mBluetoothHeadset = null;
            }
        }

        @Override
        public void onServiceConnected(int profile, BluetoothProfile proxy) {
            // TODO Auto-generated method stub
            if(profile == BluetoothProfile.HEADSET) {
                mBluetoothHeadset = (BluetoothHeadset) proxy;
                }
            }
    };



    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
    mBluetoothAdapter.getProfileProxy(this, mProListener, BluetoothProfile.HEADSET);

   }

I have reference the following, but I don't know how to continue. How to get bluetooth connected devices using BluetoothHeadset API

Second question:

Where should I type the List<BluetoothDevice> devices = mBluetoothHeadset.getConnectedDevices(); in??

Third question

Can I click the device which list by getConnectedDevices() and operation after I click such as setOnItemClickListener ??

I'm new to this. Thanks for everyone's direction.