During the purchase process you will be asked if you have a keycard. To do this, enter the 23-digit number (01-xxxx xxxx xxxx xxxx xxxx-x) that you can find on the keycard. You can top up the ticket on any keycard - even from other ski resorts.
You can keep this card saved in your user account and do not need to enter it again next time.
No. You only need a key card.
Your order (= booking) is saved on the servers of the ski area. When you first pass through the turnstile in the ski area, your keycard (= ski card) is read and the server is asked whether you are authorized to do so. If so, the purchased ticket is transferred to the card and the turnstile on the lift opens.