If your phone fails to boot or is stuck in a boot loop, a clean IPSW install can revive it.
Unlocks Hub themselves include a disclaimer: “This YouTube channel does not promote illegal unlocks. This video is for genuine people who have forgotten their Apple ID password. Using or unlocking any device which does not belong to you/lost/stolen is a punishable offence. Do not use any methods for illegal unlocking as such device can be traced.”