No. Applicants must apply to the three university courses as early as possible and upload any unconditional offers they receive to the online application system.
No. Your Chevening application does not constitute an application to an individual university for your selected course. You will need to visit the individual university website and apply directly to the university for your selected course(s).
You must contact the British embassy/high commission to discuss this directly. It is at their discretion to agree alternative courses that may better reflect your new career focus.