Credit Card Lounge

I went to the mall recently and got a simon mall visa debit card and it says on it accepted anywhere that visa credit card is, so does that mean i can buy things online using this debit card even in smaller online stores that accept visa, not big stuff like amazon?

Im going through an old purse and I have 2 visa credit cards how can I tell if they are still usable? Exp. dates are still good.