Ask Tuntunba #04 What is the Ruling on Reciting Fatiha During Prayer?

Sheikh, what is the ruling on reciting Fatiha during prayers? Do we recite it in every single rakah of every prayer? Do we recite it in Nafl? Do we recite it silently in Nafl or out loud? What if the Nafl is done at midnight, should we recite it loud or silently? Do we recite it in obligatory prayers when behind the Imam? What happens if you forget to recite Fatiha in prayer 1) when you're alone and 2) when you're behind the Imam?