Only roms based on stock can be installed on locked bootloader.
Custom kernel needs to be compiled using a specific sony key to run on locked bootloader (which we don't know and no way sony will release)
Sent from my C6602 using Tapatalk
for FM maybe try this http://forum.xda-developers.com/showthread.php?p=58366301#post58366301
and to install this rom Just boot to recovery and flash this rom then flash kernel from recovery also
and it should boot just fine