To be quite honest yes you can but they have to be of value meaning back to being perfect mint condition they have to be wanted by the buyer depends on which Pokemon series you actually have really really they do buy them but it depends on the buyer and the condition of which you have
Short answer, yes. But if you'll get more if you sell them on your own or trade them in.
Yes
YES, Be sure to Shop them around to the different dealers to get the best price.
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