Does a person need to fast for gallbladder function tests such as ultrasound,x-ray etc..?

Yes, usually: The gallbladder contracts in response to certain stimuli, most physiologic is the presence of food (fat) in the stomach/small intestine. However ultrasound, looking for stones, is best done when the gallbladder is full, of bile, so that the ultrasound waves can penetrate into the gallbladder. I noticed that you are jaundiced, at your age, this needs immediate attention. Please see a liver doctor