Here are some cheats and tips for the game Dreamcast (hardware).
In-game reset:
Press B + Y + X + A + Start during most games to reset the system.
Delete internal memory settings:
Hold A + B + X + Y and turn on the Dreamcast. Release the buttons
after the date/time prompt appears.
Alternatively, hold B + X on controller B and turn on the Dreamcast.
Release the buttons after the date/time prompt appears. Note: This
will not affect your VMU memory and will only reset internal
information, such as date, time, and Dreamcast Network settings.