After you purchase a valid license and notify us that you need to have an older version, you will get access to all installation files till the requested version - Q2 2012 SP2. With this version you will find all files needed to work in WPF 3.5. Again I would like to remind you that this version will not be supported by us in any way.
The SourceCode for the controls shipped with version 2012 Q2 SP2 will not be the latest one, it is the one for that specific version. There are some controls that we introduced after this version, with our most recent versions.
All new controls, features and bug fixes are available with our latest version - Q1 2014, which would be also included in your license.