Concerning the 4th commandment, it was not commanded to keep at the time the 10 commandments were written by the finger of God. Notice that is says "Remember the Sabbath day..." not commanding to do so, but commanding us to remember to do so. It was commanded to keep on the seventh-day of creation. The 10 cmmd's were written on stone by the finger of God, this alone tells me it was important and wouldn't be a temporary thing. When I say something is set in stone, I mean it's steadfast and sure, not temporary and unstable. Now talk about sinning? What is it? 1 John 3:4,5 says what sin is... "Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law. And ye know that he [Christ] was manifested to take away our sins; and in him is no sin." So if sin is breaking the law, and if you think the law is not valid anymore, then are we are all free to sin? Of course not.
Ecclesiastes 12:13 "Fear God, and keep his commandments: for this is the whole duty of man." The whole duty of man does not change. It is the same now and will be the same in heaven. Jesus is our example it says in the Bible and we should follow his footsteps, and did Jesus keep the law? Yes, John 15:10 "I have kept my Father's commandments, and abide in his love."
What should you do if you love God? Keep his commandments! 1 John 5:2 :By this we know that we love the children of God, when we love God, and keep his commandments."
Read also: "He that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him." 1 John 2:4