1. Do I need to unlock bootloader if I want to update it to Stock 4.3 Android (I mean Android 4.3 from Vodafone-Germany) ?
2. My phone custom number is 1266-2257 while the phones from Vodafone-Germany 1266-0537 is it imporant and it makes me unpossible to update?
3. (Below) Is this proper way to update phone by flashtool? [If not please give me step-by-step tutorial that will not brick my phone]
1.how to install the newest Android 4.1.2 for Sony XPERIA T LT30p
a) first of all, check your firmware version (if you already have the newest one, you do not need this tutorial)
b) download and install latest Flashtool from here (mirror)
c) download also latest Android 4.1.2 (mirror) for Sony XPERIA T LT30p
d) paste the ftf file downloaded in step c) to folder „Firmware“ included in the XPERIA Flashtool
e) open the XPERIA Flashtool, click on flash and choose downloaded firmware, than click ok. Important - if you do not want to delete any data of your phone, just uncheck flashing userdata.sin file. All data will remain in your phone, but sometimes it can cause additional troubles. So it is better (and I recommend that) to do the backup of your personal data, than proceed with clean instalation and then restore your personal data.
f) turn off your phone and when Flashtool shows pop up window, connect phone to PC with holding volume down button
g) after few minutes all is done and your phone gets the new firmware
PS. Now I'm running Windows 8.1, I know I can install drivers anyways but to be sure I'll install on second HDD Windows 7.