IF A TORAH COMMANDMENT APPLIES TO US TODAY WE MUST KEEP IT
We are responsible to obey all of the Torah we think applies to us today. The ten commandments define sin - in order to commit sin we must transgress one of those commandments. For example - if I refuse to love my neighbor as myself I would be committing sin even though that is not one of the ten commandments.
By refusing to obey I would be making myself god (ruler) before God and thereby breaking the first commandment.
John stated explicitly -
1Jn 3:4 Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law.
The only way to commit sin is to transgress the law because that is what sin is - transgression of the law.
If a Torah commandment applies to us today we must keep it.
The key is to understand that not all of Torah applies to us today - to know what does apply start with the New Testament and let it speak to you....
Keep the ten commandments and then grow from there.