Well in the first place you have to use the Desktop CD/Download program for prior years. So you can have 2021 or any year Desktop program open on your computer at the same time.
Online is only good for 2022 right now until mid Oct 2023. You can be logged into online and have the 2021 Desktop program open at the same time.
You can buy the last 3 years of Turbo Tax here,
https://turbotax.intuit.com/personal-taxes/past-years-products/
You will need a full Windows or Mac to install it on.
