Originally Posted by NicolasMMM
Well, there is a custom recovery, ROM and kernel. Or it seems to be so (about the last one). But I never unlocked my bootloader, although I tried with many procedures. Is it possible I unlocked it without wiping everything? And how can I check it?
yes you could've, there's a fuse editing method that doesnt wipe internal data.
in order to check if its unlocked, turn off your phone. hold vol - button and plug in charge cable. you should be in s/w upgrade screen; in upper left corner you'll see that your bootloader is unlocked
if you hadn't unlocked bootloader, you would've softbricked the device while isntalling custom rom.
To install custom roms on O4x:
1. upgrade to jb
3. unlock bootloader
4. flash custom recovery (cwm)
5. flash roms
6. if you encounter any issues, search, they've been answered already.