They are as follows:
v1: 2016 (2015 builds) - introduced Apple Carplay
v2: Early 2017 MY (2016 builds) - introduced Android Auto
v3: 2017/2018 (2017+ builds) - introduced Marketplace/OTA app updates
v4: 2019 (completely different) - new system / introduced OTA firmware updates
Of them, v3 and v4 have some capability to receive updates over the air although success rates (based on forum posts here) is eh...
Any updates available to v1 and v2 will need to be done at the dealer or by using one of the other methods above.