I've stopped an update of OS X in the middle! Now all I have when I boot the system is the normal beep sound of
POST for hardware check.
I've found a link that's been mentioned Apple has released a flash version of firmware update but for mid-2015 macbook 15 inches.
Now I'm stuck I don't have access to anything! I have access to an iMac in case needed.
Could someone lead me to a right direction? How should I restore the firmware?