Hi,
You will still have to sit AS exams at the end of your first year at college. Don't forget, your course could be linear or modular (linear = AS doesn't contribute to the final A-level grade, modular = AS does contribute to the final A-level grade). Even then, your AS grades are what your teachers will use to decide on your predicted grades, which are the grades that get sent off with your application to university. In terms of resitting, you can resit AS exams in your second year, but you will also be studying for your A2 exams in the second year, so it depends on if you will be able to handle the workload. Meanwhile, for A2 exam resits, it depends on your college. My college does not offer A2 exam resits, so if I wanted to retake my A2 exams, I would have to do it with an external centre. But at the end of the day, it depends on your college and their policies, so maybe ask them if you are seeking clarification.
Best of luck.