NAVTEQ, the software maker, and Alpine, the hardware maker, don't give you an option to revert the software updates. To begin with, Acura does not give you a DVD with the old navigation software/data and all the old information is erased when installing a new version. Follow the installation instructions very carefully or you can messed up your navigation system and it will cost you to send it to Alpine to try to fix it. Definitely don't turn off your navigation system power while the software is installing, read the warning/directions carefully.
Even if you have the old DVD, the old DVD will be ignored because NAVTEQ does not allow to revert back to older versions.
Though, if there is a non-documented way to start a revert process with an older DVD version, it may come useful at some time or for somebody. Do you have any more details..?
If you ever want to load your old nab disc back to the MDX there is a way to do it. I know you need to hold down 2 buttons near the knob that will let you revert to the old version disc.
2011 Pearl White MDX Advanced
... OEM towing, 20 mm wheel adapters,
... rails/crossbars, black wheel well trims,
... side windows acrylic deflectors,
... Michelin Latitude Diamaris HP 285/45R19,
... Full size spare tire,
... 6000 Kelvin HID's
2010 Acura TL Tech.
2001 Mercedes ML 320
2005 Mercedes ML 500 AMG Package