If understanding the concept of how the Law functions like a Constitution and goes through changes--with certain parts applying for a time and then becoming void when a new part of the Law becomes accessed, it helps greatly in understanding how it flows. When God said "Thou Shall Not Murder", that is something that never changed. However, the legal system for dealing with that law did transform in the NT...as well as the means by which one could fulfill that command since the LAW in the OT could never give any kind of hope to others in actually being able to keep it fully without the power of the Holy Spirit.
Some branches of Christianity teach that the ethical Law remains, while the civil/ceremonial statutes have been done away with. For Gentiles, this may seem a satisfactory solution to the problem of Torah...but for Jewish believers it isn't so simple as that....all supposed abrogations can be otherwise explained within the Jewish framework for understanding Torah. Some rules were transformed by their fulfillment...a process already found in the Tanak, for example, when the Tabernacle was superceded by the Temple. In the New Testament, Yeshua's own sacrifical death fulfilled the function of temple sacrifice foe sin and either superceded it or changed it into a memorial...as explained in Hebrews 7:11-13 .