'B' version in the Columbus is equivalent to 'C' in RNS510, they are both LED screen versions.

I can't remember either, but I'm pretty sure once we had compatible maps installed (v5 and up) that voice command for navigation entry worked with firmware 39xx and up.

I checked mine yesterday and voice entry still works with v6 maps and 5238 firmware.

If the mic is not plugged in at all (ie only wired to the BT unit) then you wont get any commands to work at all, cant select radio, media etc it will just say, 'Pardon?' after you press the voice button. Only nav not working is a coding/compatibility issue only.

Refer to Maverick's instructions for retrofitting of mic, it has the coding instructions also:

Volkswagen RNS 510 Microphone Connection for voice control | my-gti.com

note the byte 7 coding...bit 0 should be selected, bit 1 should be delselected. Then bits 2 and 3 should be deselected to allow voice and screen input whilst moving. Lastly bit 7 should be enabled in all recent cars that support it, this puts the navigation instructions in the MFD.