Hello how are you?. I would like to ask a question, can you put a custom item for the player to buy it and after 5 seconds it disappears? How you can try grade D weapons at the grocery shop in the city of giran. Thank you very much

Yes just look how the try on xmls are made. Or do shadow or time based items. There are plenty of them already existing. just look how they work and copypaste them.

yes you can do as Finn say or too via database.