NordVPN only states in its official information that you have to enter the code once and complete the activation in one go, but not a word about a specific expiry time (e.g. 1 year, 2 years).
ORF almost always works for me. If it doesn't work, disconnect the VPN and reconnect, a server is selected at random when connecting and there is usually a new server / new IP. ORF sometimes puts known VPN IPs on the blacklist, so it can happen that a server is listed.
I was able to do a search and according to the manufacturer's information I was able to find, the plans cannot be stacked, so this would not work. I would still recommend contacting NordVPN yourself, as they manage all the plans etc. and can give you up-to-date and more accurate information.
This is a digital activation code that can be activated in the NordVPN. Unfortunately, digital products cannot be purchased in our shops without a customer account. If you do not wish to purchase the licence via your normal account, you can create a "Throwaway Account" with a new email, which you can only use for such purchases.