If I just bought stocks with cash settlement mode using DBS vickers, and have yet to settle, can I sell before I settle them? If so, how may I sell them? Otherwise, what will happen if I don’t pay for them?

Hello there! Usually a broker will give you T+3 or T+5 for you to make payment. Yes, you can sell them before the stipulated time frame. You pay the difference if you make a loss, and they will pay you the gain if you make a profit. If you dont pay them, they will sell your shares at the market price.