We still support v1.0.2005.1, but only for real severe bugs, so any things we implemented in v2.x we won't port back to 1.0.2005.1.
To get access to 1.0.2005.1, you purchase a per seat license for v2.x and we'll send you a v1.0.2005.1 license (the v2.0 license isn't compatible) and you then can download the latest build for 1.0.2005.1 from the customer area.
If possible however, we suggest you upgrade your code to 2.6. The upgrade will make you run into breaking changes though we tried as good as possible to document these in the v2.6 documentation section 'migrate your code'. You can read the documentation online or download it in the v2.6 demo.