That is perfectly fine. Some babies start walking later. If he is standing up unassisted and crawling these are good indications that he might start walking soon.

The weight gain appears to be normal. If your baby is active and eating regularly then there is no reason to be concerned.

About 8 - 9 months. Initially, they will have to start sitting with some assistance. Then they will be able to sit without assistance.

It is perfectly fine. As long as your child is active there is no reason to be concerned.

It shouldn't affect crawling. Try to keep some toys in front of her when you have give her tummy time. This might increase her interest in tummy time. When she is on her tummy try to play with her in that position. Rolling is a good sign, especially if she is doing it on her own. There are still a few months before she will start crawling on her own.

Hi introduce variety of food in the diet which baby likes and get attracted towards attractive foods like fruit custard, pudding, juices, veg upma, veg pulaao etc

If she eats with her left hand there is no need to change it. Let her use whichever hand she is comfortable with using. At 18 months toddlers will only speak a few words and this is completely normal and nothing to be concerned about. At the end of the second year children speak about 50 - 100 words. They will point and also be able to answer simple questions when asked.

Her weight is perfectly fine and there is nothing to worry about. Babies lose a little of their birth weight after being born and then gain that weight along with additional weight after that. This is the normal weight for your child. Most Indian babies are in this range at the end of the first year. It is best not to compare and also check online what the progress should be. As long as your baby is eating and active there is nothing to be concerned about.

Please get your calcium, vitamin D levels checked. If the pain is consistent you need medical attention.

The reason she isn't putting on weight is because as you pointed out is she is very active. Babies stop gaining a lot of weight after their first birthday is because they crawl and walk more than they used to. If she is eating and active there is nothing to be concerned about. This is completely normal.