What all activities can we try for baby in his 4th month, he started balancing his head 90% already ?
How many times a day do we need to give him massage and which oil would you prefer ?

Sing talk read show colorful objects, point out objects around the house give baby items to hold and explore tummy time, offer objects at a little distance to encourage reaching or even moving ahead on the tummy. Massage is your and baby's choice. You can massage even multiple times a day, each one need not be elaborate but just a gentle rub to calm and soothe the baby and on the flip if baby is not interested then you can even discontinue the elaborate massage.