Dun worry! My daughter also didn't know how to walk until after 15.5 months old. As many other parents have mentioned, kids develop at different paces; do not compare your own with the others. You never know what's better in your kid vs others...right?
Yes, I read books and took course all say that more crawling is good for baby brain development.
So no need to worry too much if can't walk by themself.
Same here, but don't worry, kids develop at different pace, some say more crawling is even better for their brain development. My boy is chubby so it's rather hard for him to find the balance. But they'll eventually get there!