Hiya,
for instrumental, because there are only 4 pieces to learn, it is most certain they will all come up on the paper obviously but in what order I am not sure. With vocal, just learn them all..
In order to revise, you should do mind maps for each piece (harmony, texture, word setting etc). hen d another mind map for the stylistic features so that you are ready,. I would also say, constantly listen to the pieces over and over again until they are completely stuck in you head so that if any part of the piece comes up, you are ready to answer questions on it. My teacher says that you should go to bed and put headphones on and listen to all the pieces on repeat whilst you sleep.
Hope it all goes well