ANSWER 03: Covenant Laws and sin
No, that is not a sin! If a person breaks any of the Laws of Sin and Death then and only then is the action (or inaction) a sin. Covenants are reciprocal AGREEMENTS. A covenant with GOD is on the order of: I will bless you in this way and this way and that way IF you do this and do this and do that. If a human breaks the Covenant by not keeping all the requirements GOD gave, then they forfeit the blessings inherent in that Covenant. It is NOT a sin, they just lose the Covenant blessing(s).
GOD made a Covenant with Abraham concerning possession of the Promised Land. Part of the Covenant agreement included physical circumcision. NOTE: Abraham already had a ‘circumcised heart’. If any descendent of Abraham failed to circumcise his son, then the son was no longer in line to receive his portion of the Land of Israel. SO, if a Christian does not celebrate the Feast of Passover it is NOT a sin. If a Jew does not circumcise his son it is NOT a sin, it never WAS a sin. A person keeps Covenant Commandments in order to stay within the Covenant and reap the promised blessings. The promised blessing for circumcision was NEVER salvation. It was required in order to be in line to inherit the Promised Land. Christians sometimes confuse the inheritance of heaven, which requires a ‘circumcised’ heart, as a counter weight to physical circumcision. The two get juxtaposed as though they were opposites. They are not opposites. Salvation (having a circumcised heart) is a requirement in order to inherit heaven. Physical circumcision is required in order to inherit the earthly Land of Israel. Both are requirements. One is a spiritual requirement and the other a physical requirement. They are not antithetical. If a spiritually circumcised Gentile wants to also inherit a portion of the physical Land of Israel, he must be physically circumcised. If a physically circumcised Jew wants to also inherit a portion in Heaven, he must be spiritually circumcised in heart. 