How reset user and password System Blue

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• RESET: It just restarts your system.
  
• BOOT0: Can be used for firmware flashing in DFU-mode over USB (see documentation).
  
• BOOT1: Hold this button while pressing reset: Either it enables a special debug mode (short press, then press it again) without hardware watchdog. Or you can reset to default settings when you hold it for several seconds (until long beep).
  

You may have to attempt a few times... this should put Blue back in 'factory' settings....