I am just back from mettupalayam. My son is now about 3 months old. One more week to complete 3 months. Now he listen well to sounds. Babies of this age should listen to sounds. He moves his head where the sound sound comes from. He focus on faces. I still wonder whether he recognize mom, dad. No idea. I read that newborn males have chance of developing hydrocele, accumulation of liquid in scrotum sac. In most babies it will disappear at about 1 year of age. If not a small operation is required, which is outpatient procedure and risk free.
He has not developed another habit. He is sucking his thumbs. Most babies start sucking thumbs even while in mother's womb. There is not much to worry about it. Babies will forget it when they are grown up.