According to Ephesians 3:2 is not this the age or administration of grace?
No. This verse tells us that a special administration of grace was given to Paul that he might preach the gospel of the administration of The Mystery. Just notice how Paul follows this statement up in verses 7 & 8. Compare with Col 1:25 where he speaks of his ministry being an administration of God to him. The next verse speaks of this ministry as The Mystery.