Your Autodesk subscription provides you access to the current version plus three versions back. If you purchased a subscription today you will have access to the 2022 software plus versions 2021, 2020, and 2019.
To answer your question directly. . .you will not have access to 2018 software if you purchase a subscription today.
Using AutoCAD as an example, when you login to your Autodesk account you will see you only have these options (as of today):