This is a late response, I know, but rewriting creatives would be hard to do for Extension 1. The Literary Worlds module in particular is really vague, so if you preprepare something, it's highly likely you'll get a stimulus that's entirely different to your story idea. Having said that, you could adapt an idea you like, but I believe creating something on the spot usually means you have a better chance of covering all the requirements for the question. For whatever module you're doing, being on top of your texts and techniques is crucial to succeeding like it is in Advanced. And it's also good if you have several ideas on what you could potentially argue, but never assume anything, particularly for Extension 1. I know it's scary having to respond to an unseen question on the spot, but trust me, covering what you need to and actually answering the question is so much better for your marks at the end of the day, in my opinion. Being open-ended with your interpretations of quotes is the best way to tackle any question the examiners throw at you, so knowing them well would be the best way to study.
Hope that helps!