Well, don't worry about putting it in reverse whilst driving forwards, the car won't let you do that - you'll just get a lovely loud grinding noise instead and the car will still be in neutral. Ask your instructor if you can take a photo of the gearknob next time you're in the car, then when you're not in lessons you can keep looking at the pic of it to learn the layout of it off by heart. Also helps to remember that the odd numbered gears are at the top, and the even numbered ones are at the bottom.