The significance of selling hedging is to lock in the sales profit in advance, not to earn more in the futures market. In fact, there is no direct relationship between buyers and sellers, and the exchange acts as a similar intermediary to supervise buyers and sellers to fulfill their responsibilities. There is a penalty for breach of contract.
Financial futures, now there are only stock index futures in China. The stock index futures contract provides for cash delivery. Therefore, the issue of physical delivery is not involved.
I won't go into details about the change of basis. To put it simply, the basis is generally changing, but the overall range is not large, and the result of hedging is generally roughly offset in the current period rather than completely offset.