FInally I was brave enough to play around my Nexus 4. Using ADB and Fastboot, I unlocked the bootloader and install custom recovery (tried both twrp and hen cwm). However when I reboot the system, it gets stuck on the flashing 4-circles screen. I had wiped the cache and others, including factory reset, but it is not rebooting.
On the first attempt , I installed twrp, it went well. During the reboot, TWRP asked if I want to unroot to which I agreed. Then that it went to flashing loop. I don't think the SU file was in the phone.
Phone is stock 4.4.2
Thanks in advance.