Must/mustn't and needn't/don't have to

This new Star Wars movie is awesome. You ... see it.

If you are not sure in your answer. You ...change your answer.

You ... play this game. I've got lots of other ones.

Your time is out. You ... answer the question.

Stop! This way is off. You ... open this door.

You can't buy this game anymore. Its date is expired. You ... download it from Playmarket.

Your friend can advise you the right way of solution but you ... take his advice.

It's a very stip cliff. You ... be careful.

You ... to answer this question within 15 seconds. This is the only condition to win the award.

The last train leaves at 5.30. So you ... be late.

This app for Ipad quite expensive because you ... pay extra for each new songl.

You ... use your mobile phone during the test. That's illegal.