But God did indeed change the law several times:
1)The covenant with Noah,
2) the covenant with Abraham,
3) the covenant with Moses,
4) the covenant with David, and
5) the covenant prophesized in Jeremiah and fulfilled in Jesus.
The New Testament is clear that the requirements of circumcision of the Abrahamic covenant and the Temple sacrifices and food restrictions of the Mosaic covenant are no longer in effect. God does change his law.
It mocks God to accuse Him of changing His mind or His law. He has not changed His law. He fulfills His Law for you in Jesus Christ. He covers the law of sin and death with His perfect blood, but He does not wipe out one yot or tittle of it. Look again at the Covenants of God. You might want to look particularly at the Noahide Covenant, since the rapture is prefigured there, according to Jesus in the Olivet Discourse.
And PS all those covenant were completed by God in Christ ...