You are unable to roll back to previous calamity versions (NOT ALL OF THEM)
As the Title said , you can no longer Backtrack to previous calamity updates , this **HOWEVER** only includes versions from **July 14 2019 to Dec 2, 2024**, versions prior to the first date and after the last date should all be good.
Versions from this timeframe lack a file called CalamityMod.csproj, this makes the process simply impossible, here are some examples :

Let's rollback to a previous version (after december 2024 example) :
 the file (COMPATIBLE)")
Now, let's Go back a bit more
 released on August 13 2022 : File is not Present ")
Even when trying to copy the file from one version to the other, compilation errors appear making it impossible to advance.
I've randomly checked versions in the timeframe and all of them seem to be lacking the file
Any Help on this ? Thanks