Hi, check to see if you can access the info from your RNS-510 itself first.
If you turn it on and hold down the setup button, it will hopefully bring up a screen like this:
The letter at the end of the delivery part no will tell you your version.
If you can't access that menu then I believe you will need VCDS to find out your version no or to enable that menu.
Also I believe that if your unit has a star button on the top right then it's at least a version C? Maybe someone else could confirm that?
Hope that helps