I've been using your plugin and quite impressed with it.
I just want to give you one suggestion that when I use "Show the answer of a question immidiatly after the user have selected an answer(Will not work in single page mode).", then if user has selected wrong answer and clicks "Show Answer", it shows wrong but user can correct his answer before clicking "Next", then we may call it cheating.
I just want to request you when user selects wrong answer and click show answer, all radio button should must get locked and answer can't be changed.
Hope you have understand what I am saying.