1. The month after the year is 120 1, which means 20 12 1. The purpose of continuity is that futures contracts will be delivered at maturity and will not be traded. The main contract will be moved back, and even the futures contract one month after the delivery month will be displayed together.
Even two, three and four are the same.
The main contract has the largest position and the most active transaction. For example, the most active rebar at present is11/kloc-0.