Here is more info and 20% off the Avid price:
https://www.sweetwater.com/store/detail/PTAUP
All purchased PT12 versions will be perpetual after they lapses unless it is a monthly subscription so yes, you can use the PT12 version that was out when your plan lapsed for ever but you still need to buy the correct update if you want to take advantageofthe annual plan and releases during said year. Next time if you renew on time ot will be 149-ish AUD for another year.