A teacher in China asked me to help with the following queries:
1) Can students ask the IELTS examiner to repeat a question?
Yes. They can say something like: "Sorry, can you repeat that please?". It won't affect your score if you do this.
2) Can students ask the examiner to clarify a question?
Not in part 1 or 2. The examiner can only repeat the same question in part 1, and refer you to the task card in part 2. In part 3, it's fine for students to ask for clarification e.g. "Sorry, I'm not sure what you mean by that". The examiner is allowed to rephrase the question in part 3. If you ask for clarification once, it shouldn't affect your score, but don't do this too many times!
3) Can students ask the examiner to define a word?
Again, only in part 3. The student could say: "Sorry, could you explain what you mean by... (unknown word)?"
4) Can students ask for more time to think?
I don't recommend doing that. Students lose marks for long hesitations, so it's best for them to practise answering quickly.
5) Can students ask to miss a question in parts 1 and 3?
They can, but they will lose points, so I don't recommend doing this. It's always best to attempt an answer.
6) Can students ask for a different topic in part 2?
No. They must take the topic card that the examiner gives them.