[Xperia Z2 General] DooMLoRD:
Basics

[ various bootmodes ]

newest Sony devices have three boot modes... these bootmodes can be reached when device is powered off...

Normal - just press power button and device starts booting

Flashmode - this mode is used to flash stock OFFICIAL firmware using flashtool, denoted by GREEN LED (this is similar to DOWNLOAD/ODIN mode of the Samsung devices)

Fastboot mode - this is a special mode, denoted by BLUE LED, used when we want to flash custom kernel, custom system images, for that we need to unlock bootloader, i will tell more details about this later...

[ various key combinations ]

this is most important part...

known key combinations so far:

while device is power

OFF

Volume Up + USB cable connected to PC -> FASTBOOT MODE (BLUE LED will light up)

Volume Down + USB cable connected to PC -> FLASHMODE (GREEN LED will light up)

while device is power

ON

Volume Up + POWER (for 10 seconds) -> resets the battery, its like removing the battery and putting it back in [device will vibrate once]

Volume Up + POWER (for additional 5 seconds, total 15 seconds) -> will power off hard, device will power down [device will vibrate thrice]

[ understanding About Phone ]

(check out attachment if the above pic is not visible)

What it all means for u:

Kernel version:

Sony has released this device with 3.4.0 kernel. When custom kernels are released (they will surely be soon) this string will change.

Model number:

The Xperia Z2 has model number as D65xx and has few models. They differ in the spectrum of frequencies supported for 3G/WCDMA http://www.gsmarena.com/sony_xperia_z2-6144.php

D6502/L39h - HSDPA

D6503 - LTE

D6543

Android version: http://en.wikipedia.org/wiki/Android_(operating_system)

Sony officially launched this phone with android version 4.4.2 (aka KitKat).

Baseband version: [linked to firmware version]

(Crudely) this is a software interface which communicates with radio -> gsm/wcdma (2g/3g)/LTE, basically acts as a base for the main OS to ‘talk-to’ the hardware on the phone [I know this explanation isn’t precise even partly incorrect.. if someone can help me out I will update it]

This is similar to the "radio" image of the HTC devices.

Build number: [aka firmware version]

This is dependent on which firmware u flash on ur phone and is linked to the baseband version.

Btw some devs use this field to add their own ‘signature’ to the ROM so if u are using custom ROMs this field might be varying. Though the Baseband version for a particular firmware remains same.

what is firmware?

The firmware is a package containing all the official software for a particular build. It will contain system, kernel & baseband files. Generally the firmware is supplied (on forums) in form of FTF package (a container file ending with .ftf) which can be flashed via FlashTool.

what are the ways to update/repair firmware?

SEUS (Sony Ericsson Update Service) / PCC (PC Companion) / EMMA are all official ways to update to new or repair existing firmware on your device. SEUS/PCC are available to all users (consumers), EMMA is special and is only available to select individuals. This requires you to connect device to PC and then the software will check for updates and download them over the internet.

Updates can also be sent as FOTA (Firmware over-the-air)/OTA (over-the-air) updates where in you can download and install the updates without the need to connect to PC/any software.

FlashTool is an unofficial user-created tool, but the best way to flash official firmwares. Generally the firmware is supplied in form of FTF package (a container file ending with .ftf) which can be flashed via FlashTool. Thus FlashTool is the easiest way to do offline updates, just download the FTF file, it keep on PC and flash ur device when ever you want to.