Selling a stock before x-dividend?

yes you can

There is no guarantee that a stock will go down by the dividend amount on x-div day. On rare occasions, it goes up more than the amount of the dividend. As example, look at the stock TPZ. On Friday it was x-div to the tune of 12 cents. The stock opened at $25.70, which was exactly the previous day's opening less the dividend, then quickly recovered - and ended the day at $25.94. If you had shorted the stock ( no options on this one ) hoping to cover on Friday, you would have lost your shirt, and then some. And you will also be on the hook for the dividend payment to whoever bought your shorted shares.

You need to know the Ex date. This is usually 2 days before the record (BC) date. So let's assume the Ex date is 10th Dec. The settlement date is irrelevant, as is the record date. You bought on 11th Dec.(which was a Saturday(??)) which would appear to be Ex Div (without the dividend). You would have to buy on the 9th or earlier to be *** dividend and then sell on the 10th or after to keep it.

I think you need to check your dates here!

If the purchase date precedes the ex-dividend date then you are entitled to the dividend. You can sell the stock prior to the payable date and still receive the dividend.