1. If you fail to fly any segment of an itinerary in the order issued, the remainder will be cancelled.

2. If you, however, cancel, what happens will depend on the conditions of the fare you booked. This could be anywhere from a full refund to your original form of payment to a credit which you can use for future travel (subject to a penalty), or to nothing.

Exactly how to best handle this is dependent on #2, so please check those conditions carefully.