Everything is basically the same year to year although there were internal changes to the S-Tronic which is the Borg Warner DL-501 dual clutch gearbox. Specifically, there were revisions to the mechatronics unit used to control the gearbox. Earlier versions B8, pre facelift, are far more prone to failure than later years. There was an update in late 2012 and again in 2014, mostly with the electronics although I have a feeling some of the solenoids were "upgraded" as well.
That's the only one I specifically know about. There were of course changes to the radio and options over the years. The B8.5 (facelift) has a more modern radio and infotainment system and from 2014 on, if you had the sport exhaust, you could set it separately from the drive mode. In the 2013 model, if you go into dynamic, the sport exhaust valves automatically open. It's tied to the drive mode unlike 2014+.