A year and four months came the Sony Xperia SP into my hands for a W Labs and then operated with the operating system Android 4.1.2 Jelly Bean, which was later upgraded to Android 4.3. Unfortunately Sony did not upgraded to Android KitKat and that was abandoned.
But today the Xperia SP and relives the news after the developer community XDA-Developers managed to make a ROM of Android 5.0 Lollipop for this model Sony.
A developer named Bagyusz XDA-Developers was responsible for carrying the ROM CyanogenMod 12 Android 5.0 Lollipop uses the Sony Xperia SP, not only managed to do that, as it has also managed to install this type of ROM bootloader 100 % blocked, making virtually anyone can install this unofficial ROM.
Just have rooted your Xperia SP, install a modified Recovery and follow the steps of the official XDA-Developers topic. That if, as is not an official ROM, there are some things still do not work equipment such as Wi-Fi, FM Radio, the NFC, the camera and you will probably find more than some unexpected reboot.
Anyway, so always start with this type of modified operating system and over time polishing the ROM developers is going to finally work nearly or almost everything.