Is my prayer valid after I forgot to bow in the Fajr prayer, then I performed it and completed the prayer, and performed the prostration of forgetfulness before the Taslim instead of after it?

In this case, it is prescribed to perform the prostration of forgetfulness (sujud al-sahw) after the salutation (taslim), according to the more preponderant opinion. However, if one performs the prostration of forgetfulness before the salutation out of forgetfulness, there is no harm in it. In any case, the prayer is valid.