Basically, yes, old notes become nonlegal tender. Hyperinflation is resolved by the government issuing a new currency (sometimes with the same name as the old

Basically, yes, old notes become nonlegal tender. Hyperinflation is resolved by the government issuing a new currency (sometimes with the same name as the old one), and allowing conversion to the new one, at whatever extreme ratio like 10e6 to 1 or whatever. The conversion lasts for a limited time and then any notes existing after that are no longer accepted as fiat currency.