[A_Thinker]

Most Christians do believe that Jesus changed those laws. But Jesus himself said:

For truly, I say to you, till heaven and earth pass away, not a jot or tittle will pass from the law until all is accomplished. (Matthew 5:18)

Most Christians believe that Jesus fulfilled (met our obligation with respect to) those laws.

Jesus also said ...

Matthew 5:17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.

As a Jew, I don't believe that the covenant of Sinai has been superceded.

The Sinai covenant hasn't been superceded ... it's been fulfilled.

[malakhi]

Verse 18 says that not a jot or tittle of the Law will pass until heaven and earth have passed away. Unless you are a preterist, you don't think this has happened yet.

Where in the Hebrew scriptures does it indicate that someone else can fulfil the Law on your behalf?

Do you believe that Jesus fulfilled all of the Law of the Torah? What about commandments that specifically pertained to women? Or married men?