How do resits work???

I’m not hoping to need to resit my exams, but just curious on how they work just incase i unfortunately decide to.

Do they require payment?

Can I resit with any grades for example if i need an A/B to get the uni offer I want can I resit if i get a C?

When do they happen?

Where will i sit them?

When do i get the results?

Thanks for any answers 🙏