They were not called Christians until after Pentecost---post crucifixion, resurrection, ascension. Those who followed Him during His lifetime on earth, His mission on earth, were under the law and the law was still in effect.
They obeyed them after the crucifixion because they were Jewish---if they did---and there is no evidence that all of them did. It was one of the things that plagued the apostolic church. Judaizers insisting that Gentile believers had to obey the Mosaic Law. A Council was held to settle the matter, and it did not just involve circumcision. Acts 15:5 But some believers who belonged to the party of the Pharisees rose up and said, "It is necessary to circumcise them and to order them to keep the law of Moses." 8-10 ANd God, who knows the heart, bore witness to them by giving them the Holy Spirit just as he did to us, and made no distinction between us and them, having cleanses their hearts by faith, Now, therefore, why are you putting God to the test by placing a yoke on the neck of the disciples that neither our fathers no we have been able to bear."
And this was the judgement at the Council. Verses 20-21 but should write the them to abstain from the things polluted by idols, and from sexual immorality, and from what has been strangled, and from blood.
There is no mention of Sabbath keeping in there and what is mentioned is not given as Law within the New Covenant. Romans 14: 4-6 it says Who are you to pass judgement on the servant of another? It is before his own master that he stands or falls. And he will be upheld, for the Lord is able to make him stand. One person esteems one day as better than another, while another esteems all days alike. Each one should be fully convinced in his own mind. The one who observes the day, observes it in honor of the Lord, The one who eats, eats in honor of the Lord, since he gives thanks to God, while the one who abstains, abstains in honor of the Lord and gives thanks to God.
I will do this in a separate post due to length, and it will have to wait until I have the time to devote proper attention to it. If you may be thinking that I will back away from this challenge, think again. I embrace it.