To reverse the game at 1x speed, users press and hold the rewind button. And at any point, releasing the button makes time goes forward again.
To avoid confusion, the display could get a sepia filter when rewinding, showing that time is moving backward.
For debugging, this method lets you do things like go back to the previous instruction (if the time information is kept) and in the same way access the previous HBL, IRQ, VBL, etc.