What is ghrelin and is it really a hunger hormone?

Yes. The discovery of ghrelin followed after the discovery of the ghrelin receptor in 1996 and was reported by masayasu kojima and colleagues in 1999. The name is based on its role as a growth hormone-releasing peptide, with reference to the proto-indo-european root ghre, meaning to grow. The name can also be viewed as an interesting (and incidental) pun, too, as the initial letters of the phrase.
Yes. Ghrelin is a hormone produced by the stomach that causes the hunger center in the brain to be activated. It is usually increased before a meal and decreases after eating. Levels are abnormally high in some obese people, but bariatric surgery may reduce levels. Increased sleep may also reduce levels.
Ghrelin is a protein. (peptide) & hormone produced in the stomach & pancreas that stimulates hunger by stimulating growth hormone from the pituitary gland. Paradoxically, obese people have lower ghrelin levels than average, & anorexics have elevated levels. Studies are showing ghrelin has many other functions such as intestinal motility, lung development in fetuses, & enhancing learning & memory.
Yes. Ghrelin is a "hunger hormone" and is actually found in elevated levels during sleep apnea.