Thank you for starting a new thread.
The Telerik Control Panel installs only official release product versions, in this case the official Q3 release and its service packs. The internal builds are distributed only as hotfixes (zip packages) and they are not detected by the Control Panel.
In your case, if you perform a 'CHANGE' operation in the Telerik Control Panel this is the same as you would go to the Windows Control Panel, right click 'Telerik RadControls for ASP.NET AJAX Q3 2012' and select 'Change'. It will perform a modify operation over the installed product.
I hope this information is helpful. Please, do not hesitate to write back if you have any further questions..
the Telerik team