Sarah and Haggar.......

If the texts in Bible were to be  100% reliable and also unambigvalent then ,  God must have given ( or promised) the Land to the grand-children of Abraham . and not necessarely to the "adherents to the religion-of-Abraham" because, at that moment of that promise it did not exist yet. What happens if and when those Grand-Children became Christians like George Habash and Edward Saiid ?? and what happens if and when those Grand-Children  became Muslim like Ismail Hanniyah ?? and what happens when those Israelis never ever were the Grand-Children ?? like Olmert, Sharon and Perez Golda Meier Kirk Douglas , Paul Neuman Sammy Davis Jr. etc...   To whom ,exactly , was this Land Promised ? and who may inherit Abraham's Land ??   Besides all that , why would God take away a Land from the Kananites-people and then give it to the Chaldeans-tribes??   Seconly why should the son of Sarah inherit his father and mother and not the son of Haggar  ?? who, indeed , was the first-born ?? !   Raja Chemayel a grand son of Haggar, Sarah was my step-grand-mother and Abraham was fully my Grand Father.