I do not recommend to follow tutorials from outside XDA since these tutorial can do damage (the ones here aswel but these are more checked and verified).
The tutorial you used required an Unlocked bootloader since you need to flash a boot.elf (kernel of Xperia SP). You've done this on a Locked bootloader and thus a softbrick.
I recommend you to repair your device with the tutorial about flashing stock ROMS see my signature..
Sony Xperia SP
12.1.A.1.205 Android 4.3.x
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