I need to downgrade my adobe flash from 20.0.0.267 to 20.0.0.228 due to my dental software. Please HELP! We can not operate functionally because of this

I have found the archived software for 20.0.0.228 and it gives me the error 1722 when i try to install it.

I have uninstalled the newest version.

What am I doing wrong.

We are using a dental software that requires the older version.