A short position is to sell an open order and then buy a closed position. It's a bearish person.

Bilateral, it should be two-way. It is bilateral when collecting the handling fee, once when opening the position and once when closing the position. Only collect open positions unilaterally.

Two-way is this market, that is, you can go long or short.

There should be T+0, t is the time, that is, today's opening, today can be even, unlimited times.