root proplem I need your help topic

So guys first I appreciate any one gonna help me

I have Xperia z c6603 4.4.4 android

I wanted to root my phone and I tried in every possible way but every time it fails
So I found a solution

P.s I don't have Internet connection for my pc

1-install super su and don't open it
2-flash old kernel so you can root
3-root your device (( in this step I tried rooting by flashtool and it did work but in the log it says root done.. rebooting device.. So I waited for 3 minutes but my phone didn't restart so i did it manually))
4-flash your. 283 kernel
5- upgrade supersu binaries so root is done

In step 4 I didn't find supersu (( which I've installed before)) but I found superuser app instead and I can't upgrade binaries or unroot or any thing. This app is useless

So i want to delete it and full root my device because in flashtool it says my phone is rooted but when I install any app for rooted devices only it says my phone is not rooted

I think maybe if I flashed an official 4.4.4 rom every thing will be normal again but I have a question. If I flashed a rom does that mean that I will unlock bootloader cause I don't want to unlock so i don't lose my be2 and drm keys

And I can't do ta raw backup (( to save be2 and drm keys)) unless I root my device

Please help me and sorry for my bad english