download generic 4.2 os ftf file from this link
https://docs.google.com/file/d/0B8hA...MycW9sV2s/edit
then download flashtools by antraoxyde from this link
www.flashtool.net/
install the flashtools, then in c drive, in the flashtools installed folder, there is a folder for drivers, install all the drivers, and there would be another folder named firmware, paste the downloaded ftf file to the firmware folder, then open flashtools, then turn off your mobile, press volume down button, then simultaneously plug the usb in, the mobile will show the green led, means yur mobile is in flashmode, then in flashtools, click left button, there will be two option flashmode or fastboot mode, click flashmode, then choose the generic os you had pasted in the firmware folder, click wipe data and cashe, click app log, means all the option would be clicked yes, then click flash, the flashtools will starts flashing the os, after the process completed, unplug the phone and restart the phone, first boot will take time to make cache files, then the cell will boot up, yes you came back to android 4.2, plz hi thanks button if i helped you, coz i am new in xda developers, and want to become senior member !