You are so off base. If in fact he was adopted his birth certificate would have the adopted parents names on the certificate and not the original parents.
And his original certificate would still be there, that is never changed.
Think it through. The document was created on a computer. They didn't have those in 1971. (not for that stuff anyway.)
Barack got the adoption annulled, sometime within the last several years.
That was easy.
That was easy.