At this point in time, the Sony Xperia M (C1904, C1905) and the Xperia M dual (C2004, C2005) sit with different Android versions. The Xperia M comes with Android 4.1.2 Jelly Bean with build number 15.1.C.1.17, whilst its dual-SIM sibling comes with Android 4.2.2 in the form of build 15.2.A.1.12 (although build 15.2.A.1.14 has been certified by the PTCRB website since the start of October).
We’re sure that at some point Sony plans to upgrade Xperia M owners to Android 4.2.2, especially since most of the work has already been done with the Xperia M dual. However, if you’re the impatient type and want to experience Android 4.2.2 now, you’ll be glad to know that the official 15.2.A.1.12 FTF firmware file can be used to flash on the Xperia M without issue. Yes, you’ll see a setting options for dual SIMs but you’ll only be able to (obviously) still use one SIM. Check out a video of this in action below (in Czech).