Most devices have the bootloader unlocked.
WILL WIPE YOUR LOCAL PHONE DATA! http://android.stackexchange.com/questions/33691/why-does-unlocking-the-bootloader-wipe-phone
Sony requires unlocking, but allows it for many phones: http://developer.sonymobile.com/unlockbootloader/unlock-yourboot-loader/ It voids warranty.
When the guide says: insert USB with sound up button clicked, it is not joking: that does put the device on a special mode. This can be seen as the status LED turns blue instead of the regular red (charging) / green (charged). It doesn't have to be at the exact same time: if you hold up and insert, it works.
TODO what is the name of this blue light mode? Is that fastboot?
Then run:
sudo "$(which fastboot)" devices
# Replace with your unlock code from the website.
sudo "$(which fastboot)" -i 0x0fce oem unlock 0x0000000000000000
Now you can remove the cable, and hold at the same time:
- power
- volume up
- volume down
buttons. And it will enter the boot screen.
Name of an SDK CLI tool.