Here you have multiple options. The best thing would be to open the item and scroll to the bottom of the item page - here you can see when the item was listed or updated. Furthermore, you can see the date on the public questions and answers. If all questions have been answered and the item does not have the "sold" label you can assume that the item is still available.
Tip: Before you ask a public question if the item is still available simply make a realistic offer, and if the seller doesn’t respond the offer is probably too low or the item isn’t available anymore.