Hi all!
This how-to applies for locked bootloader phones.
What you will need?
ICS 4.0.3 ftf:
http://www.4shared.com/rar/2Lf1ikwm/ST18i_41A0562.html
ICS 4.0.4 ftf:
http://www.mediafire.com/?2o2glqbm6oyf9m9
Root_v5 hack:
http://xdaforums.com/showthread.php?t=1600728
CWM installer:
http://xdaforums.com/showthread.php?t=1346190
Preliminary step:
= First off, install full ICS 4.0.4. You have to be on ICS 4.0.4 in order to proceed.
= The easiest way to do so is to use Flashtool to flash 4.0.4 ftf and DE-SELECT wipe data! Thus your current apps will be kept.
= By installing 4.0.4, if you had root, you will lose it. But worry not, here is what you should do:
Follow this 3-step process:
1) By using the Flashtool flash
only the kernel (kernel.sin + loader.sin) from ICS 4.0.3
= For flashtool, Unknown Sources and Debugging must be checked in phone settings
= Put the ftf file into the firmware directory of flashtool (usually c:/Flashtool/Firmware), open flashtool and select flash, then flashmode, chose the 4.1.A.... firmware and select exclude Fota, system and baseband , select 'No final verification' and DE-SELECT wipe data, cache and apps log. Click OK and follow instructions (power off phone, press volume down button and plug the usb).
2) Boot the phone and do regular Root_v5 hack + CWM installation (CWM-5.0.2.7-nAa-r2)
= When it's finished you can root with the Root_v5 tool following its instructions
= Now install CWM recovery by using the CWM Installer following its instructions
3) By using the Flashtool flash
only the original kernel from the ICS 4.0.4 provided ftf.
= For flashtool, Unknown Sources and Debugging must be checked in phone settings
= Now do the same operation as 1) with 4.0.4 ftf file and you're done.
Enjoy!
p.s. Thanks to Frakkia and others for useful tips.