The best way to explain why there are changes in dietary law, circumcision, and other such things is found in Romans 7:2
Released From the Law, Bound to Christ
7 Do you not know, brothers and sisters—for I am speaking to those who know the law—that the law has authority over someone only as long as that person lives? 2 For example, by law a married woman is bound to her husband as long as he is alive, but if her husband dies, she is released from the law that binds her to him. 3 So then, if she has sexual relations with another man while her husband is still alive, she is called an adulteress. But if her husband dies, she is released from that law and is not an adulteress if she marries another man.
4 So, my brothers and sisters, you also died to the law through the body of Christ, that you might belong to another, to him who was raised from the dead, in order that we might bear fruit for God. 5 For when we were in the realm of the flesh, the sinful passions aroused by the law were at work in us, so that we bore fruit for death. 6 But now, by dying to what once bound us, we have been released from the law so that we serve in the new way of the Spirit, and not in the old way of the written code.
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Living by the Spirit in the new covenant isn’t exactly a stroll in the park. You must forgive those that ask for forgiveness - just like Jesus forgave us by the washing with his precious blood. We can not deny that Jesus is God in public. We are not to love this world. We are forbidden to sleep with prostitutes (non virgins sleeping around):
18 Run from sexual sin! No other sin so clearly affects the body as this one does. For sexual immorality is a sin against your own body.
19 Don’t you realize that your body is the temple of the Holy Spirit, who lives in you and was given to you by God?
Once again - the old covenant is still there. The law is still there. There are Jews still waiting for their messiah to show up after 2000+ years of waiting - and they are keeping the Torah. But in Christ we are not bound by the law. Therefore, if I have some pork I know Im not condemned nor am I dis obedient to Christ. Pork may not be very healthy - but flesh in general counts for nothing. Spirit gives life:
John 6:63
The Spirit gives life; the flesh counts for nothing. The words I have spoken to you—they are full of the Spirit and life.