After 15 years of the spreading of Christianity, the Jerusalem church still suggested ongoing education at synagogues on the weekly Sabbath rather than church on Sunday, and they still fully endorsed the law of Moses the modern church calls 'a curse' and 'bondage'. Why does the modern church have such different standards than those that KNEW Jesus personally?

Why is Christianity zealous on preserving the 'Ten Commandments' even though it rejects the Sabbath commandment?

What should one infer about Christianity given the fact it emphatically rejects the SIGN that Yehovah ordained to identify his people?