Yes u can

Generally No, but you can choose social science before grade 12 exams even tho u chose Natural back in grade 10. But in some universities you can switch fields, example is AAU. Not just from natural to social but from social to natural if your matric score is good enough. I was allocated to social science by NEA but easily switched back to natural.

Yes you can I was a natural science student and I changed to social science when we were choosing university placement so unless they change their minds you definitely can

No