You are under the impression that the "old covenant" and the renewed covenant are separate rather than a planned and connected continuation -- a software update if you will, that was preset for after the resurrection.
A renewed covenant would be the same as the old. What we have now is not the same. If it is not the same, it is new.
You misunderstand how we as commandment keepers live out the Renewed Covenant. We live it the same way the disciples did after the resurrection-- by guarding and keeping the commandments of life. Walking the Way that Jesus walked, since he is the Way, the Truth, and the Life and he kept the commandments faithfully in his obedience to the Father.
But do you keep them?
You’re referring to the disciples in Jerusalem, right? They were Jews, the law of Moses was their national culture, they weren’t required to change that. It wasn’t the same for gentile believers. Gentiles were never commanded to be circumcised and keep the law of Moses.
If we are "under the old" because we obey the Word, which in it Yah tells us many times to observe to keep it forever throughout our generations, then is that also your assertion of the disciples after the resurrection?
If you are not a Jew, God never told you to observe it throughout your generations. That is narsigesis, you’re reading yourself into the text.
26For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins, 27But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries. 28He that despised Moses' law died without mercy under two or three witnesses: 29Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace?
Do you not see how the Sinai covenant is being contrasted with this new covenant in this very passage? They are not the same or renewed, they are separate and distinct from one another.
Hebrews 10:28-29 KJV
[28] He that despised Moses' law died without mercy under two or three witnesses: [29] Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace?
“He that despised Moses' law died without mercy under two or three witnesses...”
“The blood of the covenant, wherewith he (Christ) was sanctified...”.
Two different covenants are being compared and contrasted here.
What is sin? See 1 John 3:4
Sin is transgression of the law. To which law is John referring? I’ll give you a hint, he tells us in this same chapter, 19 verses after this one.