Does the babies (under 6 mts & on mother feed) who fed more frequently gain more and r more healthy as compare to ones who demand less frequently.

Babies are different. Even at that very young age, babies have their own personalities and likes and dislikes. Some babies are big eaters a few times a day, others are "grazers" who like to snack small amounts all day. The end result - weight gain, adequate growth, and appropriate development are the goal, and these can be achieved with either type of feeding. In the end it's the calorie intake a day that counts.
Breast feeding. It doesnt necessarily mean that more frequent feeding will give you a more healthy child.
Not necessarily. If the baby is content with the breastfeeding routine in that he gets exactly how much he needs, he may grow equally well with that who feeds more frequently.