Why is it that you think that just because Jesus only mentioned a few of the commandments to the rich young ruler that that means we don't have to follow the others. You are making assumptions. If you want to confirm whether God deleted some of the commandments you would have to read other text to find this out. Of course there is not one text in the Bible that tells us that some or all of the law has been done away with.
Jesus mentioned the few commandments that the rich young ruler was keeping. If you cannot give up your riches for the Lord that is considered worshiping other idols. Jesus then asked him to give them up, but he could not.
The same Jesus that only mentioned the few commandments here also said in Matthew 5:17-19, "Think not that I am come to destroy the law, or the prophets; I am not come to destroy, but to fulfill. For verily I say unto you, Till heaven and dearth pass, one jot or one tittle shall in no wise passs from the law, till all be fulfilled. Whosoever therefore shall break one of these least commandments, and shall teach men to do so, he shall be called the least in the kingdom of heaven; but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven."
Till heaven and earth shall pass. If you think the law is done away with just look into the heavens and then stomp your foot on the ground. If both are still there, so is the law!
Psalm 111:7-8 says, "The works of his hands are verity and judgment; all his commandments are sure. THEY STAND FAST FOREVER AND EVER, and are done in truth and uprightness."
Romans 7:12 says, "Wherefore the law is holy, and the commandments holy, and just, and good.
Psalm 119:172 says, "My tongue shall speak of thy word: for ALL thy commandments are righteousness."
John 14:15,16, 21 says, "If ye love me, keep my commandments. And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever; He that hath my commandments, and keepeth them, he it is that loveth me: and he that loveth me shall be loved by my Father, and I will love him, and will manifest myself to him."
1 John 5:2-3 says, "By this we know that we love the children of God, when we love God, and keep his commandments. For this is the love of God, that we keep his commandments: and his commandments are not grievous."
God says "If you love me keep my commandments." He did not say if you love me keep some of my commandments.
The main problem with what you are saying is the same problem I have seen many times. You are only taking a couple of texts to support your point. When we study the Bible we need to incorporate all the Bible texts not some of them. That is how we get misinterpretations. We are not to intrepret the Bible ourselves. As we further read and study the Bible will interpret itself.
Do not be deceived by the devil. You are doing exactly what he wants you to do.
God is love. God is the law.