firmware for xperia M2 Dual :
to download android 4.4.2 click her .
to download android 4.3 click her .
to download android 4.4.4 click her .
to download android 5.1.1 click her .
after you download the firmware change .rar or .zip to .ftf
flashtool for xperia M2 Dual :
to download flashtool for windows click her .