I have 4 worlds already and wanted to delete one, all worlds I've gotten items that I brought back to my first world. I'm just wondering if I delete a world would the items I received will stay?
Items within a world are self-contained, and unaffected by the deletion of their source. Items held by a character are also self-contained, and are unaffected by the deletion of their source. If you delete a world, all items within that world will be deleted, but a character holding items from that world will keep their items. The same can be said for another world containing items obtained from the deleted world; all items within the world will remain (except for those held by characters).
Edit: The contents of piggy banks and safes are character specific, can be accessed from any world using the same character, and remain attached to the character regardless of a world being deleted. Thanks, Ben Ong.