Yes, you still need to identify three university courses, although you can enter the unconditional offer as the first of your three options.
No. Chevening Awards are aimed at graduates who have already acquired some work experience. You must have already graduated from your degree at the time of application.
No, Chevening Scholarships are available for study in the UK only. It is also not an option for you to start your studies in your home country through distance learning and then to come to the UK to complete the course later in the academic year.