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Any Advice on Cross-Examination?

I have my case coming up – this is the 2nd PO order and custody in 10 years – it never gets any easier.
Here are my questions:
1) The Social worker report (s132) – she has just re-iterated much of what the ex has already said, but then says things like the childrens’ answers “did not–appear to be coached or rehearsed.? Has she any qualification to say this?
2) The lawyer for Child – again pretty much asks questions based on what he has heard in the court and states same sort of thing – same question as above really?
3) Am I able to cross-examine LFC?
4) Am I allowed to just ask pages of closed questions requiring yes / no answers?
5) Can I ask that my McKenzie friend puts the questions to my ex on my behalf?
6) I understand that I am only allowed to examine my own witness of info they have already submitted, is that correct?

Thanks in anticipation?