What was prophesied in the Abrahamic Covenant and how was it fulfilled in Christ?

A messiah was promised based on Abraham's willingness do as God had asked (told) him to do. This included leaving his home country and going into a different land, trusting God regarding an heir, and then offering his only (legitimate) son as a sacrifice.

The promises God made to Abraham are unconditional and everlasting. There are no "if" clauses in the Abrahamic covenant.

This covenant promises land  (Gen 12:1, 13:14-18), descendants (Gen 12:2) and blessings (Gen 12:3). Gen 15:3 promises that all nations of the earth will be blessed through the seed of Abraham. This is a foreshadowing of the coming messiah that Christians believe is Jesus Christ. The Abrahamic Covenant finds its ultimate fulfillment in connection with the return of Messiah to rescue and bless His people Israel. (http://www.gotquestions.org/Abrahamic-covenant.html)

Christians believe that Christ is the fulfillment of the promises God made to Abraham

(Gal 3:29 KJV) And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise.

(Gal 3:7-8 KJV) Know ye therefore that they which are of faith, the same are the children of Abraham. {8} And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed.

15 The angel of the Lord called to Abraham from heaven a second time 16 and said, “I swear by myself, declares the Lord, that because you have done this and have not withheld your son, your only son, 17 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 cities of their enemies, 18 and through your offspringb all nations on earth will be blessed, because you have obeyed me.” (NIV GEN 22: 15-18)

"That the blessing of Abraham might come on the Gentiles through Jesus Christ, that we might receive the promise of the Spirit through faith" (Galatians 6:14 NIV).

The Jews are still awaiting the messiah to come and restore Israel. Christians believe the messiah (Jesus glorified) will return in "glory" to set up his righteous kingdom on earth.