Hi Well done on monitoring your child's development. As put know child's development is a sequence and a pattern. Most children follow it but not all. There can be exceptions where child can skip a development only to achieve it later If her development has been fine all this while, meaning,  she grasps things, puts it in her mouth, holds her head, able to blabber words like mama , dada and has no other issues, you can wait for another month. If there are any concerns plz see your pediatrician Hope this helps Dr siddarth warad Dr bear clinic

He will be sit.. do physiotherapy and try to sit with support..

Can wait for next 1 month and observe in not work visit developmental pediatrician