It is impossible to be under 2 covenants at the same time . The writer of Hebrews is very clear for those he was writing to.
The same goes for us . When a person is born, he is under the weight of the law that requires perfection . The law was ceremonial , moral and sacrificial.
Heb 10:9 Then said he, Lo, I come to do thy will, O God. He taketh away the first, that he may establish the second.
The first covenant was replaced with the second or new covenant.
You can’t be under both at the same time . If you remain under the first , your destiny is hell.
If you believe in the second by faith and turn from this life in repentance, you will live .
I heard a person the other day, try to bring the requirement of the law (which leads to death) back on the back of new covenant believers.
This is very dangerous.
Christians have been freed from the curse of the law.
We are required to love God and love neighbor perfectly in the New covenant! And guess what ? We can’t do that either !
Praise God , Jesus did, and because he did, I am covered by the blood of the new covenant.

Can’t have it both ways..