I bought a plane ticket, but the duty-free shop couldn't find the flight information. You can consult customer service to change the flight information, which will not affect the pickup. Duty-free shops stipulate that you can buy them 60 days before returning to China, but you'd better call the airline to confirm the flight.
When buying goods on the duty-free shop software, be sure to fill in the departure time, flight number, ship number and train number. You can't mail them, but there are pick-up points at airports, railway stations and ports. If everyone's quota and quantity of goods are limited, then it is forbidden to buy.