God's plan is eternal, and God's grace is unchanging. Israel was God's sovereign choice to be a light for the entire world to know there is a God of salvation. God's plan for Israel and the nations has been joined from the beginning.
God is able to do all things. God has been dispensing HIS grace from the beginning, and salvation has always been, and will always be, by God's grace through faith.
Acts 15
5But there rose up certain of the sect of the Pharisees which believed, saying, That it was needful to circumcise them, and to command
them to keep the law of Moses.
6¶And the apostles and elders came together for to consider of this matter.
7And when there had been much disputing, Peter rose up, and said unto them, Men
and brethren, ye know how that a good while ago God made choice among us, that the Gentiles by my mouth should hear the word of the gospel, and believe.
8And God, which knoweth the hearts, bare them witness, giving them the Holy Ghost, even as
he did unto us;
9And put no difference between us and them, purifying their hearts by faith.
10Now therefore why tempt ye God, to put a yoke upon the neck of the disciples, which neither our fathers nor we were able to bear?
11But we believe that through the grace of the Lord Jesus Christ we shall be saved, even as they.
12¶Then all the multitude kept silence, and gave audience to Barnabas and Paul, declaring what miracles and wonders God had wrought among the Gentiles by them.
What do you make of verse 10 ?
I would say things are different by the time you get to Acts 15 from before.