How many teachers are asking you the questions?
The task specifies that you have to have a 'panel' of teachers, so it could be anywhere between 2-5. Usually, there are 2 teachers who are members of the panel (based on my friends' and my experience).
Is it between you and teacher?
It depends on your school, but most likely it's just between you and your teachers.
Is it between you and other english teachers or english ext 2 teachers only?
Again, depends on your school, but most likely it will be the ext 2 teachers.
How long is the presentation?
Presentation is between 15-20 minutes. You get some of the questions they'll ask you beforehand so you have a bit of preparation, but some are on the spot and are usually very simple (they ask these to clarify your work).
What happens if you stumble? (I stumble with my words all the time) Do you lose marks?
Unfortunately, yes. One of the marking criteria is 'presents highly developed responses that express complex ideas with clarity and precision.' So you need to articulate yourself quite well if you want to get in the highest range.
With regards to your creative writing, it's a difficult skill to master and English teachers often beat around the bush when giving feedback, etc. The only real way to improve creative writing is to practise and get good feedback to improve. Be familiar with language devices and all that jazz, as this will improve your writing heavily. (It's also especially important to have a fair level of creative writing as the new English syllabus with mod 3 may ask you to write an imaginative piece). If you want feedback on some of your written work, just send it through to me and I'll be more than happy to feedback.