Apple re-issues iOS 9.2.1 to fix iPhones bricked by Error 53

Apple today re-issued iOS 9.2.1 to fix the "Error 53" that had crippled iPhones whose owners had replaced some parts themselves or had a third-party shop do repairs.
The new iOS 9.2.1 will only be served to users who update their iPhonesthrough iTunes on a Mac or Windows PC. Most iPhone owners retrieve updates over the air using their cellular connection, and so will not receive the replacement.
Error 53 appeared on iPhone 6, 6S, 6 Plus and 6S Plus devices after a do-it-yourself or third-party