1. Short answer: If you purchase a wireless headset AND the remote answering accessory you will be able to automatically answer calls from the headset. The wireless will pickup the line that is ringing. If you want to switch back to different lines or transfer you will need to perform that function on the buttons of the telephone.
2. If you choose to purchase a wired headset you will need to press the "line" you wish to answer. Then you can talk through the headset.
Note: To see how you can pickup a call using a wireless headset see video demo below.