What to do with UCAS application wrt sitting papers at a different centre

I’m a 2023 leaver taking a gap year + reapplying this year. I’m also resitting as an external candidate next year, I spoke to my school on results day and asked if I could resit in school next year as an external candidate. They said to ask them again in October to see if they’ve got space, if not I’ll have to find another centre (I’ve emailed them now, they just haven’t got back yet).

I’m an early applicant so I need to send my application by the early deadline, if my school doesn’t get back to me in time I will have to apply to resit in another centre that has space and that lets me apply online I assume? I want to ask, will I have to put this centre on my UCAS application before sending it off?

The reason I ask is because on the application it says to put the centre where you studied and the dates between which you studied at the school, obviously I’m a gap year student so I’m not studying but my careers advisor (not connected to the exams office, they are under the impression I’m resitting with school) told us to put 2024 as the date when we finish school as we’ll be awarded the grade through sitting in the school. However this other centre I’m thinking of isn’t a school where you study it’s just an exams centre, would I still have to put that I studied there like I did with my school, does that apply to all centres?

How does this work also in terms of predicted grades, can I get predicted grades from my school whilst also resitting at a different centre or does it need to be from the same centre?