As meditrina says, the school must answer any reasonable question you ask to help you prepare for your appeal. They cannot, however, give you any personal data. That includes information that allows you to identify who it is about indirectly, as well as information that names someone.
They will certainly include in their case information about the number of children in the year to which you are applying (which must be at PAN or above since they are refusing to admit your child) and the numbers in other years (at least, a total for the whole school if not a breakdown by year).
They should be able to tell you what categories of children were admitted during the normal admissions round and the distance from school for the last child admitted (assuming distance is the tie breaker), but I doubt they will want to give you more detail than that.
If this is, as meditrina speculates, an in-year admission, the categories of children admitted and the distance for the last place offered are unlikely to be relevant. If you think a child was admitted from the waiting list when your child should have been at the head of the list, that would certainly be relevant. But how places were allocated initially won't have affected your application. The only question for an in-year application is whether there was a place available and you were the highest priority applicant according to the school's published admission criteria.
If this is not an in-year case, I am intrigued as to why it is happening now (too early for the 2021 admissions round, late for the 2020 admissions round) and why there was a long battle.
If you would like to tell us more about your case you will get some good advice on here.