Here are some updates from the adopter:
Quack is getting better on his own. He has gained more confidence and has started to roam freely in the house. He will go out to the kitchen whenever he feels hungry and even eats at the common kibbles place.BUT connection with me and other human? Still a NO. I don't think he is fierce. I think he's afraid of human presence. His relationship with other cats is ok, no hissing. and still his favorite place is under my bed!