Clarence and Richard. In Shakespeare, Richard has Clarence killed, drowned in a cask of wine. Clarence's death is actual in history, but not for the reasons Shakespeare. Actually Richard supported Clarence, who had with Warwick betrayed his brother. In the movie, it is Buckingham who suggests that Richard pretend not want to be king.
Rivers is governor to the prince.
Edward's marrying her outraged the nobility and Warwick especially, who was arranging a marriage for the king. He subsequently switched sides in the war. In the movie, it is Hastings whom Richard threatens with his withered arm. Historically, Hastings conspired with the Woodvilles against Richard. Historically she was in France at the time of the action, but her presence here is seen as a spokesperson against Richard.