4 months postpartum. Till what period?

Having Diastesis Recti 3 finger wide, 2 finger mark depth. My body structure is thin and muscular but  having big belly. The Belly still looks like 5-6 months pregnant.  Age 32 yrs, height -160 cm, Weight 58 kgs, Slim body with no other medical history / disease/ allergy. All good. 1. What exercises, food, other things to follow to reduce belly and Diastesis Recti? (vaginal delivery)  2. What all blood tests are generally required post partum?  3. Have low breast milk, due to which baby cries and have to give formula milk from 1 st week itself. How to increase breast milk? 4.  Suffering extreme hair loss from last 15 days ie almost After 3 months post partum . What vitamins to add/ along with what supplements should I take to reduce hairfall?   5. I have been taking  Ferronia XT for Iron, Calcium:Supracal 2000 from pregnancy time and multivitamin A to Z started after 4 weeks of delivery till now.  Please suggest if any modifications required? What to take and till what period?