Concerning everything that has been said since last I posted in this thread:
We are not under the law, are dead to the law, and are delivered from the law (Romans 6:14, 7:4, Galatians 2:19, Romans 7:6) as concerning condemnation; and therefore there would be no condemnation if we violate certain laws because it is as if the law is not there, as concerning condemnation.
However, this applies only to those who are born again; and those who are born again have the love of the Lord shed abroad in out hearts (Romans 5:5) so that we would not be disobedient to the commandments of Jesus.
However, if we mess up or blow it, provision has been made in the blood of the Cross so that we are forgiven if we mess up or blow it.
Again, this is as concerning those whose inclination is to want to be obedient; those who are born again of the Holy Spirit.
As concerning whether or not we should abide by the Old Testament or the New;
I believe that the OT applies to those who think that they can be justified through law-keeping, works, or personal merits; as well as the moral tenets in the NT. For such, it is required of them that they be perfectly moral according to every law from conception into eternity if they are going to enter in to heaven that way (Galatians 3:10, James 2:10, Matthew 5:48).
For those who are in Christ, we have been delivered from the law; even the letter of the requirements that are written down; and are set free to obey the spirit of what is written (Romans 7:6).
What this amounts to is that if we walk not after the flesh but after the Spirit, the righteousness of the law will be fulfilled in us (Romans 8:4).
However, this is a righteousness apart from the law that is nevertheless attested to by the law and the prophets (Romans 3:21) that it is righteousness indeed.
It is accomplished not through attempting to obey a set of do's and don'ts; but rather as we deny the flesh and are obedient to the Spirit, our resulting behaviour is seen by the Lord as being righteous according to the law.
For there has been a change in the law when there was a change in the priesthood (Hebrews 7:12).
So now, it is no longer the Old Testament law that defines sin for the believer; but the law of the Spirit of life in Christ Jesus; or the law of faith; is what governs the believer so that he walks in the morality that God has placed on his heart and mind (Hebrews 8:8-10, 10:16).
It is laid out in the following scripture.
Gal 5:16, This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh.
Gal 5:17, For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would.
Gal 5:18, But if ye be led of the Spirit, ye are not under the law.
Gal 5:19, Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness,
Gal 5:20, Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies,
Gal 5:21, Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.
Gal 5:22, But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith,
Gal 5:23, Meekness, temperance: against such there is no law.
Gal 5:24, And they that are Christ's have crucified the flesh with the affections and lusts.
Above is the New Testament law as concerning behaviour.