[Q] How to go back to Stock official ROM sony xperia z1 topic

I'm on ihackers 2.1 ROM android 4.3
rooted
unlocked bootloader

I wanted to go back to stock to C6902_14.2.A.0.290
I found the method but I'm not sure if this is the right way http://lionking853.blogspot.co.uk/20...rmware-on.html

and if it is the right way, after going back to stock ROM, will my phone unroot and relock again?

Can I just go ahead and do this or must I relock bootloader first?

please help me since I never done this before, only rooted and unlock that I did.

Thank you so much folks