Is it prescribed to repeat the prostration of forgetfulness (sujood al-sahw) if the first prostration was not valid, such as when the forehead was raised off the ground? And is the prostration of forgetfulness prescribed to correct a melodic error (lahn) in Al-Fatihah before bowing (rukoo’)?

If lifting the forehead from the ground during prostration means merely touching the ground with the forehead without pressing down, then the prostration is sufficient according to some scholars. Even if it is not sufficient and is repeated, the prostration is valid. As for an error in Al-Fatiha, if it changes the meaning, then the prostration of forgetfulness is legislated for it. If it does not change the meaning, then it is not legislated, and your prayer is valid in both cases.