A. The return mode of transportation is not relevant, express mail is also possible, but all in accordance with the Commodity Inspection return mode declaration, to provide the Commodity Inspection Certificate of Quality, choose "return goods" (exchange mode) export. In this way, with the original return export declaration, in the declaration of good pieces of import, you can choose "no cost offset", free of import tariffs and VAT.
B. In your case, because you have not yet gone through the procedures for the return of goods, so in the return of exports, it is recommended to choose the port where the goods have been declared for export, to maintain the same import and export bank.
C. And now your good pieces have arrived, but the return of export procedures even on the commodity inspection time is estimated to be 3 weeks, it is recommended to ask the good pieces of the customs of the port of arrival now, like you want to do no cost of offsetting the goods, can not be temporarily imported first procedures, then with the return of the export customs declaration write-off. But my experience shows that it is more difficult to estimate; now the trouble is that the good pieces have arrived, if the customs do not agree to temporary import, only to return the good pieces or tax the import of good pieces.
Supplementary answer 1: the operation of the customs return is recognized in all major countries, and the customs clearance procedure in the destination country like this is to be taken care of by the customer, talk to them clearly, they will take care of it; we should know that, globally, going out to some underdeveloped countries, the customs clearance procedure is not too much more stringent than China's countries, don't worry about it.
Yes, in order to operate a no-cost offset import, you must first have a record of the return of exports.
Returned for export, you need to go through the commodity inspection and return procedures, that is, to apply to the Entry-Exit Inspection and Quarantine Bureau of Inspection and Quarantine inspection to prove that the quality of the goods, the need to be returned, the commodity inspection certificate issued by the commodity inspection, and then returned from the Customs and Excise Department for export.