Is it permissible to pray on the second floor of the mosque, following the Imam, whether one's position is ahead of or behind him, and is it valid for women to pray there?

There is no objection for men and women to pray on the second floor of a two-story mosque, as long as they are aware of the Imam's movements. However, it is not permissible for a congregant to pray in front of the Imam, unless there is an excuse such as the mosque being too small or similar reasons.