Originally Posted by alpi123
Could i root my phone to stock android? Could get theme like the original xperia z2? When i try to install flashtool it says NSIS error, if i root my device will i lost all of my data? Could i remove the root and get back to my android 4.3?
I'm not really sure if you mean "flash" by "root" but yes. You can flash any stock ROM as long as your bootloader is locked. Your data will be wiped and you will no longer have root access.
It will be like a brand new phone.
Go check some guides on how to flash back to stock with flashtool.
Use Google for NSIS error fix. I think there are alot of guides aswell.