Twin Galaxis purposely created a seperate 'legacy' leader board to put his scores on, so that they were able to give him back his scores as part of a settlement without actually reinstating his score on to the proper leaderboards.
Very little because it's clear Mitchell aggressively sued and/or threatened to sue both Twin Galaxies and Guinness to an egregious extent and the reinstatements were minimal, reluctant and only done to finally get him to stop the constant legal harassment.
Frame by frame analysis by multiple independent experts of the videotape of Mitchell's Donkey Kong record clearly shows he cheated. I don't think anyone (who isn't Mitchell, his lawyers or few friends) has any doubt Mitchell cheated and has repeatedly lied about it.
