SCR-HD: Come in 1st in a race against SCR-HD. SCR-HD appears randomly, so it's good to do this when you first start the game up; when there are less characters and you have a higher chance to unlock the robot.
Super Sonic: Select the Chaos Emerald gear as Sonic. As the Chaos Emerald board is unlockable, and Super Sonic is considered just Sonic with the Chaos Emerald board in game, see below on how to on how to unlock the board.