Qn 1. When was the promise of the Spirit made to Abraham and why ?

After Abraham was tested on Mount Moriah, the angel of the Lord called to Abraham from heaven and said, “I swear by myself, declares the LORD, … I will surely bless you and make your descendants as numerous as the stars in the sky and as the sand on the seashore …Your descendants will take possession of the land … and through your seed (meaning Christ ) … all nations on earth will be blessed …” ( Gen 22 :16 – 18 ) ‘ … Abraham and his offspring received the promise that he would be the HEIR OF THE WORLD, through the righteousness that comes by faith.’ ( Ro 4 : 13 )
How can all this be humanly possible, if it is not for the Spirit of God ? How can Gentiles be reckoned as Abraham’s descendants, if the Holy Spirit doesn’t impart the faith of Abraham to them ? ‘This mystery is that through the gospel the Gentiles are HEIRS together with Israel, members together of one body and sharers together in the PROMISE ( of the Spirit ) in Christ Jesus.’ ( Eph 3 : 6 )
He redeemed us inorder that the blessing given to Abraham might come to the Gentiles through Jesus Christ, so that by faith we might receive the ‘PROMISE OF THE SPIRIT.’ ( Gal 3 : 14 )