God's Covenant ? Is he immutable?

Question

Geneses 17:1-16
“17:10 This is my covenant, which ye shall keep, between me and you and thy seed after thee; Every man child among you shall be circumcised”
Can someone explained to me please. If God is so immutable (unchangeable) as most Christians are trying to portrait him, than how come circumcision is not necessary for Christians?
When people bring the argument that Jesus fulfill the law or anything similar to that they are misleading others. Covenant is not a law. There is a huge difference between law and what god promised.
As far as we can see, few thousand years before Jesus even showed up in the picture god makes promise to Abraham. And as anyone who reads Geneses can see that god did not asked anything in return from Abraham and his future children’s except circumcision for this covenant. Whatever law Jewish people create in the name of god later on has nothing to do with this covenant.

. Many Christians today are crying that Jews murder their own god and God broke covenant with them. So to outline the Question… If god makes the promise and than for whatever reason he decides not to keep the promise does it still makes god immutable? Isn’t that a scary thought that whatever god promised to Christians he will change again in the future? (Just cause someone will come up with another interpretation?)
When answering this questions please look at what god promised to Abraham. Any personal convenient interpretation … what they would like… not of an interest.

Answer 1

There were two covenants for the people. The first covenant was with Abraham and his offspring. The other with Jesus.

After the death and resurrection of Jesus, the new covenant took over.

Christians are not required to be snipped because it is not a sign of their covenant. Their sign is a circumcised heart. It is changed when you ask Jesus to live inside of it.

The Law came into being with Moses and the promises that God made with the nation of Israel when he liberated them from Egypt.

God did not break the covenant with Israel, he still has promises to keep with them. But he did fulfill the terms of the law with the death, burial, resurrection of Jesus, who by living a sinless life, fulfilled the terms of the law, and allowed the new covenant to be established.

And in accordance with His word, God will fulfill the covenant with his church, the Christians.