Is the fiancée sinful for not wearing the niqab before the engagement, and is the fiancé responsible for her uncovering her face, and what is the ruling on her frequent solitary travel?

A wife's obedience to her husband in what is right (ma'ruf) is obligatory from the moment of the marriage contract, and she sins by disobeying him, except in refusing travel and consummation until he pays the dower. It is obligatory for the wife to obey her husband's command regarding the niqab, for in matters of scholarly disagreement, obedience is due to those whose obedience is enjoined, such as a father or a husband, as long as their command does not lead to something unlawful.