Knock yourself out!
As for me I am under the Covenant of Grace - the one established by the blood sacrifice of Jesus on the Cross.
If you choose to approach God under the Mosaic Covenant that is your prerogative - it is still in operation.
However, if you are under the Covenant of Moses and choose to stay there you cannot be under the Covenant of Grace as well - the shed blood of Jesus Christ is not available to you, you are not covered by the blood of Christ, and there is no justification for you on the basis of that shed blood.
The result is that you will be judged according to the full body of the Law of Moses - to the last jot and tittle!
Since no human being in history has ever kept the Law apart from Jesus Christ Himself you will, accordingly, be judged to be a sinner with the appropriate penalty.
I am a sinner too, but the essential difference is that I am justified, not by my own merit (I would irrevocably doomed if that were the case), but, by the blood of Jesus Christ. Justified solely by the blood of Jesus Christ.
Look at what the Apostle Paul says about those who believe they can be Christians and yet follow the Law of Moses:
Gal 3:1-29
1 O foolish Galatians! Who has bewitched you that you should not obey the truth,[a]before whose eyes Jesus Christ was clearly portrayed among you[b] as crucified?
Is Paul upset, or what!
2 This only I want to learn from you: Did you receive the Spirit by the works of the law, or by the hearing of faith?
Obviously not by the works of the law - lets read on!
3 Are you so foolish? Having begun in the Spirit, are you now being made perfect by the flesh?
4 Have you suffered so many things in vain—if indeed it was in vain?
Again Paul is not mincing his words here.
5 Therefore He who supplies the Spirit to you and works miracles among you, does He do it by the works of the law, or by the hearing of faith?—
Again there is no mixing of the law and the hearing by faith.
6 just as Abraham “believed God, and it was accounted to him for righteousness.”[c]
7 Therefore know that only those who are of faith are sons of Abraham.
Faith is the only thing that can justify
8 And the Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel to Abraham beforehand, saying, “In you all the nations shall be blessed.”[d]
9 So then those who are of faith are blessed with believing Abraham
And justification by faith is the only way - and it has been the case all through biblical history
10 For as many as are of the works of the law are under the curse; for it is written, “Cursed is everyone who does not continue in all things which are written in the book of the law, to do them.”[e] 11 But that no one is justified by the law in the sight of God is evident, for “the just shall live by faith.”[f]
Couldn't say it better myself - no one is justified by the law - now or ever
12 Yet the law is not of faith, but “the man who does them shall live by them.”[g]
13 Christ has redeemed us from the curse of the law, having become a curse for us (for it is written, “Cursed is everyone who hangs on a tree”[h]),
In this way Jesus Christ fulfilled the law on our behalf so that those who accept the saving work of Jesus Christ on the cross would not be cursed and condemned according to the righteous requirement of the law but would instead be justified according to the blood shed by Jesus Christ on that cross.
14 that the blessing of Abraham might come upon the Gentiles in Christ Jesus, that we might receive the promise of the Spirit through faith.
The Holy spirit is the seal of our salvation - and that salvation is through faith
15 Brethren, I speak in the manner of men: Though it is only a man’s covenant, yet if it is confirmed, no one annuls or adds to it. 16 Now to Abraham and his Seed were the promises made. He does not say, “And to seeds,” as of many, but as of one, “And to your Seed,”[i] who is Christ.
Self explanatory
17 And this I say, that the law, which was four hundred and thirty years later, cannot annul the covenant that was confirmed before by God in Christ,[j] that it should make the promise of no effect. 18 For if the inheritance is of the law, it is no longer of promise; but God gave it to Abraham by promise.
Hhmmm... so the law cannot change the fact that justification is by faith and that the law cannot justify and that the inheritance promised to Abraham and fulfilled in Jesus Christ cannot be obtained from the law
19 What purpose then does the law serve? It was added because of transgressions, till the Seed should come to whom the promise was made; and it was appointed through angels by the hand of a mediator. 20 Now a mediator does not mediate for one only,but God is one.
21 Is the law then against the promises of God? Certainly not! For if there had been a law given which could have given life, truly righteousness would have been by the law. 22 But the Scripture has confined all under sin, that the promise by faith in Jesus Christ might be given to those who believe.
23 But before faith came, we were kept under guard by the law, kept for the faith which would afterward be revealed.
24 Therefore the law was our tutor to bring us to Christ, that we might be justified by faith.
Yes, the law had a purpose, brilliantly explained by Paul. All it does is convict us of our sinfulness and convince us of our inability to escape our sinfulness (we were kept under guard). However through Jesus Christ, justification by faith is offered - and that faith is the faith in the efficacious sacrifice that Jesus Christ made on the cross. Nothing else!
25 But after faith has come, we are no longer under a tutor.
Nothing plainer - we are no longer under the law - not one part of it, nothing, nix, nada!
26 For you are all sons of God through faith in Christ Jesus.
27 For as many of you as were baptized into Christ have put on Christ.
28 There is neither Jew nor Greek, there is neither slave nor free, there is neither male nor female; for you are all one in Christ Jesus.
29 And if you are Christ’s, then you are Abraham’s seed, and heirs according to the promise.
Heirs according to the promise - that is justification by faith.
Nothing to do with the law!
It is your eternity - nothing could be plainer...
