EK doesn't (generally) sell tickets where you can use the coupons out of sequence.
Miss one and the whole ticket is cancelled with the applicable fees.
The applicable term is
Article 3.4 of the EK Conditions of Carriage:
3.4 Sequence of Flight Coupon use
3.4.1 Your Ticket is valid only for the carriage recorded on the Ticket, from the place of departure via any Stopover(s) to the final place of destination.
Your Ticket will lose its validity and will not be honoured by us if all of the Flight Coupons are not used in the sequence stated in the Ticket unless:
3.4.1(a) the fare already paid for the Ticket is the same or more than the fare applicable to the carriage which results from the out of sequence use of the Flight Coupons;
3.4.1(b) or you have paid any fare differential required for payment by Article 3.4.3
3.4.1(c) or a separate fare has been collected for the unflown sector(s).