No. You already paid RM2100 liao, worst is RM2100 => RM0.

If the share price dropped, you're only making a 'paper loss' as long as you didn't sell it. But if you sold it at the dropped price, then you're making a 'real loss'. You don't hav to pay any losses to the bank if you're not using margin financing :-)

need to ask your dealer to came out cheque for you

I've never day trade before, so I can't answer your question regarding that. Perhaps some day trader here can help you.

In regards to your losses, you don't have to pay anything extra because you only loose your own money. T+3 doesn't apply to you if you trade with your own money.

u can trade regardless of how many money inside ur trust account... but at T+3 lets say u dun have sufficient money to clear they amount that u have bought, then they will either force u to immediately bank-in some money or they will sell the share on ur behalf... profit/loss u bear ur own...
ur money will be immediate moved into ur trust acc once ur bank-in money has been confirmed... this is called cash upfront... u just need to bank-in into their respective bank acc... they dun give u their acc no#?