Normally 24 hours. Normally the stomach recovers after 24 hours. However, if you are taking narcotic pain medications these drugs can continue to upset the stomach in the absence of anesthetics.
Depends. This depends on what surgery you have had. Direct surgery on the stomach itself could result in slower return of function over several days. With surgery in other parts of the abdomen, the stomach may return to normal in 24 hours. If you had a long operation, operation with many internal abdominal adhesions, or a long anesthetic, then again it may take some days for the stomach function to return.
Incorrect. There are no changes in stomach function after anesthesia. What is important, however, is that you abstain from food or drink for at least 8-12 hours prior to surgery and anesthesia. The reason for this is due to the fact that during general anesthesia you lose airway protective reflexes, such as the cough and gag reflexes, that help to protect your lungs against aspiration.