Use this if the phone is stuck on the logo, won’t start, or you forgot the password.
Bricked devices, downgrading OS versions, or repairing persistent system errors. how to reset blackberry 10 os to factory settings
A black screen with a red LED light may appear. Keep holding until you see the “BlackBerry” logo with a progress bar. Use this if the phone is stuck on
Here’s a clear, step-by-step guide you can use or share: downgrading OS versions