[Xperia Z3 Compact General] alexaka1:
self made guide for noobs like me

i tried using this method, but it didn't work for me

what I ended up having is kernel being 291, but build still said 575 and I also lost root. and the OTA update is no longer showing up on the phone

I have a twrp backup in place, hopefully by doing a reset will get me to square 1 and not like I don't know square 'bricked my phone'

Edit: so managed to restore square one with twrp. I got scare though since my phone got stuck at the t-mobile screen, then i pressed down and power, and ut booted into safe mode (didn't know it was possible), so I did a restart then it was fine, booted up fine and everything, got root restored and now both rom and kernel are 575, thank god

I'm now having router problems so I can't download the new OTA, but I'll install it the official way than if I still require root for my daily tasks I'll try this 576-291 flashing trick.

WHEN FLASHING always click NO if it asks you to run an fcs script!

Edit2: so here's what I did:

starting state: 575, root, unable to update firmware through phone software update menu (reboots into update, update stops, phone reboots normally, gives error message about firmware update (even when phone unrooted))

-went to supersu, full UNroot, reboot, then reboot again (just in case).

-On PC with sony companion app updated the firmware to 291 build (phone shuts down, updates, updates the apps for compatiblity, phone boots with new firmware)

-phone off

-FlashTool: flash kernel.sin(575), unplug, boot phone, (close Flashtool program, it's said to interfere with the root proccess)

-install.bat, phone boots into recovery, flash supersu (navigate to supersu zip and install)

-while still in twrp, phone off

-Flashtool, flash kernel.sin(291), unplug, boot phone

-supersu starts and handles last steps (should be automatic, (it may ask to update su binary, press yes, reboot phone))

-enjoy 291 root.

tips:

before you do anything you should put a supersu zip in your internal memory, you'll need to navigate to that zip file in TWRP to install supersu

google supersu zip twrp, any version will do, or just download.chainfire.eu/1001/SuperSU/UPDATE-SuperSU-v2.78-20160905010000.zip

You (may) need the Sony PC companion app to update the firmware, officila sony site and google should help you

support.sonymobile.com/global-en/tools/xperia-companion/

you'll definetily need FlashTool (flashtool.net), download for your OS, read FAQ on site on if on win8 and above, to disable driver checking, then after you did those steps install drivers:

after flashtool installed, navigate to install folder, drivers directory, launch flashtool-drivers.exe

checkmark flashboot, flashmode drivers, and your phone's driver (to me xperia z3 compact), next

it should start doing stuff, another installer will start (that is normal), accept everything it asks you and click next until it's done, it should give feedback with all drivers having a green checkmark (for win8.1 which I have), you're good to go (red X means it faild to install, you may have driver checking enabled, refer to the FAQ on the .net to disable that)

the two kernel zips, you have to rename to .ftf, and when flashing (click lightning icon, flashmode, ok), set path to ftf files, you need to exclude the boot.xml files, at least I guess you should, only have kernel.sin in file list before pressing flash

message to OP: if you could put a similair 'guide' into installing this whole thing into th first post, I'm sure other noobs like me will appriciate it. thx