I say, and with God's help: The original ruling is that the foot is considered 'awrah (a part of the body that should be covered) due to the temptation involved in exposing it, and there is no need to uncover it in front of non-mahram (those who one can marry) individuals. As for covering it during prayer, it is not obligatory due to the lack of 'awrah in necessity and the difficulty of covering it during prayer, and there is no temptation in that. And God knows best.