Was He Legally Adopted?

Birth certificates are SEALED when adoptions take place. Barack Obama, while living in Indonesia with his mother and step-father, went by the name of Barry Soetoro. Was he legally adopted by Lolo Soetoro? Was his name legally changed or did his parents falsify his school documents? This could be the explanation for the absence of any original birth certification. Has anyone ever asked? Has he ever answered? What are the implications of an adoption to an Indonesian father? Would his U.S. citizenship have been relinquished?