Yes, after the "latest price" and before this latest price, there is a bid, which is based on the time, price and quantity of pending orders. At this last point, the transaction price is a price.

2. If the transaction price of tick(i) is 2000.2 and tick(i+ 1) is 2000.6, then if I make a transaction within 0.5 seconds between two ticks, is it possible that my transaction price is 2000.4? It depends on your quotation and quotation time. There are still bids based on the time, price and quantity of pending orders. Based on the principle of giving priority to time and price, your quotation may end in April 2000. Most of them are sold at your quotation.