Not Sitting up. Advice for all points.

Dear doctors, my baby is in his 10th month now. 1. He is doing only Army crawling and not started the classic crawling with knees and arms yet. 2. HE IS NOT SITTING UP ON HIS OWN. When we make him sit, he is sitting and that too while eating or only for a few min. 3. He has recently started pulling up and holding objects and getting up. 4. We have a walker and he is scooting in that but when we make him walk holding our hands, he is not walking and instead wants to go to army crawling again. 5. He is not staying at one place even for a second and doesn't prefer to sit but wants to keep moving on his tummy. 5. I'm worried if his hips and legs have enough strength to independently SIT or STAND. Please advice for all points.