Does forgetting the first tashahhud and standing for the third rakʿah, then remembering it and performing it out of forgetfulness, necessitate a prostration of forgetfulness ( sujūd as-sahw) before or after the salām?

If you forget the first Tashahhud and then sit for the Tashahhud after the third رکعة due to forgetfulness, you should perform the prostration of forgetfulness (Sujud as-Sahw) before the salām, because you omitted the first Tashahhud and added a Tashahhud in the wrong place. However, if you are a follower (Ma'mūm), you are not required to perform the prostration of forgetfulness, because the Imam bears it on your behalf, as stated in the Hadith: "There is no forgetfulness (Sahu) upon one who is behind the Imam. If his Imam forgets, then it is upon him and upon those behind him."