Is a large khimar that covers the shoulders and chest sufficient for hijab, or must the chest be covered with something additional, and is it permissible to wear it if it is common in the country?

If the headscarf is large and covers the woman's shoulders and chest, so that it does not reveal the details of her body, then it is sufficient, provided that it is not an adornment in itself. And if it covers the head and neck, and the woman is wearing a loose dress or a wide abaya that does not describe the body, then this is also sufficient.