Is it permissible to pray in the underground expansion of the mosque designated for women, which is located behind the Imam's mihrab on the ground floor, knowing that it is out of necessity?

It is permissible to pray in the aforementioned place (in front of the Imam) out of necessity and need, without any dislike (of the act). This is the position of the Maliki school and the statement of many scholars, and it was favored by Sheikh al-Islam Ibn Taymiyyah for those who are unable to pray behind the Imam due to crowd or other reasons. Similarly, it is permissible to pray on the lower floor, following an Imam on the upper floor.