Are older versions of MS SQL Server DEVELOPER edition now free? Microsoft SQL Server Developer Edition is now free  https://blogs.technet.microsoft.com/dataplatforminsider/2016/03/31/microsoft-sql-server-developer-edition-is-now-free/

I see that I can download 2016 and 2014, but are there downgrade rights to use 2012 and earlier versions?
No, free is not backwards compatible.