You resorted to Assumptive Reasoning, which in this case is a rationalization regarding being free to murder and commit adultery, etc.

Assumptive Reasoning does not overthrow the evidence and facts of Scripture.

What you fail to understand is the changed nature of a Christian due to the indwelling of the Holy Spirit. You don't need to tell a Christian not to murder or commit adultery, for a Christian has no desire to do those things. These are works of the flesh. Christians produce the fruits of the Spirit.

If you see a "Christian" going about murdering people, you can be assured that is not a real Christian.

Of course not... It defines what is sin. The New Covenant is not a license to sin.

Romans 6:15,16

"What then? Shall we sin because we are not under law but under grace? May it never be! Do you not know that when you present yourselves to someone as slaves for obedience, you are slaves of the one whom you obey, either of sin resulting in death, or of obedience resulting in righteousness?"

TRY READING THE BIBLE TO FIND OUT.

Read Matthew 7:12 and see.

Every society develops morals and ethics regardless of what gods they believe in or don't believe in. These rules help us live in harmony with each other and the basic ones - don't kill, don't steal, don't lie and leave other people's spouses alone - are common to just about every society. All the rest of them about not worshipping different gods, not making images, keeping the sabbath holy and coveting are religious rules and do not apply to people who do not follow that particular religion.

There are laws enforcing the rules about killing, stealing, lying, raping etc and you are required to follow them. There are no laws in civilised societies about worshipping gods, going to church, not taking photographs or buying lottery tickets. The Ten Commandments do not apply, the normal rules of civilised society do.

Jesus taught most of the 10 commandments except "Remember the Sabbath Day". However the OT was "written for our learning...", Romans 15:4.

Yes, that’s what it means.

Then you also get rid of the promises, the prophecies, the Genesis stories (including original sin), etc... But the better question is which version of the ten commandments? The version you mentioned or the version in Exodus 34 that tells us to keep the feast of weeks and not to boil a goat in its mother's milk. This other version also being called the ten commandments and chiseled into two stone tablets after Moses breaks the first set when coming off the mount to find the people worshiping a Gold Calf. Remember though, the Bible contains no contradictions.

Christians use the Old Testament for two things.

1. It's a mine for prophesies for Jesus to have fulfilled, even if you have to twist one or the other to make it fit.

and

2. When they can't find something in the New Testament to back up their prejudices, they'll look in the OT. When it comes to the Mosaic Law they pick and choose.

You don't get a pass on 'not' following the 10 commandments because their principles are contained within the Two Greatest Commandments.

Matthew :36“Teacher, which is the greatest commandment in the Law?”37 Jesus replied: “‘Love the Lord your God with all your heart and with all your soul and with all your mind.’ 38 This is the first and greatest commandment. 39 And the second is like it: ‘Love your neighbor as yourself.’ 40 All the Law and the Prophets hang on these two commandments.

The OT laws which do not apply to Christians are to do with the rites and rules listed in the Books of Leviticus and Numbers, such as to do with animal sacrifices and sacrificial offerings, ritual cleansing, clean and unclean foods, etc.