13 month 15days boy diet. About food?

My son weighs 9.36kgs, with 75.5 height. His current diet for 24 hrs is two times nanpro 3 formula total 300ml, two times dal rice, one spoon dry fruit powder, biscuits or bananas or some snacks. He doesn't eat anyother food. In order to get him to eat other foods, we consulted a dietitian whose prescribed a peptide based diet with is peptamen jr instead of nan pro3 & lupizyme plus syrup and almost same diet for 4-6 weeks excluding milk(lactic), wheat, multigrain completely from diet. I have the following doubts: 1. Is he underweight, height ??? 2. Is this correct course of action & NECESSARY??? 3. my son has only 2 teeth as of now, will cutting down on milk( following peptide diet) slow teeth & bone strength ?? 4. How to introduce other foods like curd, veggies, chicken??? 5. What is lupizyme plus syrup for ??? 6. What if my son doesn't go with peptide diet as he is very picky about food ????