[Q] What is the biggest mess I can make with my phone? And how to prevent it. topic

Hey Everyone
I have an HTC Sensation, HBOOT 1.27.0000 with 3.32 ICS Firmware, sim unlocked. I have decided to upgrade it to Kitkat, I'm noobe, So I'm just searching to gather information by now. I think I must install CyanogenMod 11.
I think the progress should be:

1. Unlock bootloader (using fastboot)


2. Get root access


3. S-OFF (Using Juopunutbear S-OFF for HBOOT 1.27.0000)


4. Wipe data, cache, and dalvik cache (I don't have enough information about this step, that what will happen after this step)


5. Flashing Rom (Which will be CyanogenMod 11)


6. Flashing GAPPS (which will be an extra step, but I will do it)

I need to know that what are the possible risks, and how can I prevent them. will I loose SIM unlock? (Here in XDA, many people said no, but a few people mentioned that it can be possible. So which one is true?) How can I backup SIM unlock? How can I backup current Rom on my phone and be able to restore that backup.

Any kind of help will be appreciated :)