[Xperia Z1 Q&A, Help & Troubleshooting] Andee23:
Hello everybody,

I'm new to all this stuff (I've never rooted or flashed my device before) so I would be really glad if someone could take their time to explain some things to me :)

About a month ago I decided to, after some time of consideration, upgrade the firmware of my Xperia Z1 to Lollipop (I previously had KitKat 4.4.4 installed). I upgraded solely because I wanted to be able to move apps (not just pictures and videos) to my SD card, which was, as we all know, something we couldn't easily do in KitKat without rooting. Even though I disliked basically everything else about Lollipop (including the new all-too-bright UI design, the unnecessarily large app icons and the lockscreen notifications) I decided to update to Lollipop, just to get the additional SD card functionality. I thought: "Oh well, I'll get used to it" and "It's probably something I can adapt to."

So I updated the firmware to Lollipop - and what a big mistake! HAHA, it's ludicrous! My device has become awful as its battery is draining super fast (from doing nothing but the regular stuff I've always done on my phone - and sometimes - from doing basically nothing at all), and as the device gets overheated all the time (again, from just doing the normal stuff - and sometimes - from doing absolutely nothing). Very soon I decided to do a factory reset, hoping it would change things. It didn't. I'm still experiencing annoying power draining issues and ridiculous overheating issues on my Z1.....

So, lately I've been reading and watching a lot about stuff like rooting, flashing and custom ROMs - things I barely knew anything about before. And what I'm currently thinking about is to flash my Z1 with the KitKat firmware I had prior to updating, so I can make things the way they were before (in other words: I want to downgrade the firmware). And then I think I'll install a custom ROM like SlimKat or iHackers to make my Z1 perform even better than before, and to get all those other benefits you get from rooting (like all those added features and settings, yay!)

Alright, so that was a bit about the background and the reason I want to do this...and here comes the questions I have right now:

Do I need an unlocked bootloader in order to flash my Xperia Z1 C6903? Sony's webpage about flashtools says that I need a unlocked bootloader in order to flash, but I've read on threads here on the XDA Xperia Z1 forum that I don't...what is right?

What are the right tools to flash my device and where do I find them?

Does it matter what/which build version I choose to flash to? I'm currently running Android 5.0.2 (14.5.A.0.270) and I want to downgrade to Android 4.4.4 and, if it matters, the version I had before upgrading to Lollipop. I think it was 14.4.A.0.157 but it might as well have been 14.4.A.0.108 or something else.

I'm asking all these things is because I really want to minimize the risk of bricking my device or causing any damage to the device that could have been avoided whatsoever. I've read many threads here on XDA, watched videos on YouTube among other things, but I'm still not sure about the things I asked above. Thanks in advance for being helpful! :good:

Best regards,

Andee23