Is it permissible to recite behind the Imam, and what is the ruling on the prayer if something other than Surat Al-Fatihah is recited behind him?

It is not permissible for the congregant to recite anything other than Al-Fatihah behind his Imam in a loud prayer. If someone does this out of ignorance, there is nothing upon him, but he must not repeat it in the future, as it contradicts the saying of Allah the Almighty: "And when the Qur'an is recited, then listen to it and pay attention that you may receive mercy." (Al-A'raf/204), and the saying of the Prophet (peace and blessings be upon him): "Do not do so except for the Opening of the Book (Al-Fatihah), for there is no prayer for one who does not recite it."