Did God change between the Law and the Age of Grace?
God did not change between the Law and the Age of Grace. He brought in the Law for Israel, then brought in the Age of Grace as a different administration. The operations changed, but the same God remains, working all in all. The change concerns operations, not God's nature.
Les teaches that after Israel was brought under Law, the Age of Grace came with the Gospel that anyone—black or white, rich or poor, Jew or Gentile—can enter God's salvation by simply believing the Gospel. This had never been on the planet before, and it is a different administration. So there was a change of operations, absolutely, but God has not changed a bit; He is the same God who worketh all in all. The context also says the manifestation of the Spirit is given, not asked for, and divided to every man as the Holy Spirit wills.
And there are diversities of operations, but it is the same God which worketh all in all.