Jesus said nothing about the Sabbath being kept in Matt 24.
There is no evidence of this in Scripture, in fact, Paul said he did not keep the Law when he was with the Gentiles.
The four laws were not Kosher laws. Kosher is Talmudic and did exist until long after the first century.
No, he did not cut his hair in Acts 21 because he was not taking a vow. Are you really that un-knowledgeable of the requirements per the Mosaic Law?
The vow that the four men were taking had nothing to do with "Temple Law". These men were not Levitical priests.
The law was done away with, per Paul. There are not two laws. There is only one Law - the Law of Christ which is His Gospel. The Law of Moses passed away, was set aside, was vacated per Paul.
So much here you posted to correct...so little time...
Will now just address what is bolded above.
Here are the four prohibitions to those goyim who feared God crowding into the synagogues...
1.
abstain from food polluted by idols - Leviticus 17:8-9 "Say to them: 'Any Israelite or any alien living among them who offers a burnt offering or sacrifice and does not bring it to the entrance to the Tent of Meeting to sacrifice it to the LORD--that man must be cut off from his people.' "
To guard carefully against idolatry, this command was interpreted by the Jews to prohibit eating any meat that had been offered in a prohibited manner. In Rev. 2:14, 20 the words of Jesus show agreement with that interpretation.
2.
from sexual immorality - Leviticus 18:6-26 lists a wide range of sexually immoral activities and ends with, "The native-born and the aliens living among you must not do any of these detestable things,"
3.
from the meat of strangled animals - Leviticus 17:13,15 "Any Israelite or any alien living among you who hunts any animal or bird that may be eaten must drain out the blood and cover it with earth,
"Anyone, whether native-born or alien, who eats anything found dead or torn by wild animals must wash his clothes and bathe with water, and he will be ceremonially unclean till evening; then he will be clean." These were interpreted by the Jews to prohibit eating the meat of strangled animals.
4.
and from blood - Leviticus 17:10 "Any Israelite or any alien living among them who eats any blood--I will set my face against that person who eats blood and will cut him off from his people."
http://fogwhistle.ca/acts/evidence.html
So actually what was prescribed there to refute those Jews who insisted Gentiles had to be circumcised to not only be saved but associate with them was something that was already set into place long ago when the church was still in the wilderness as st Stephen so eloquently put it...
3 of these 4 prohibitations merely affirm dietary restrictions as they always were for the Gentiles...
Now goyim could hear Moses preached to them every Sabbath as James said to better understand why a man had to die...and how He could defeat death...and now they too could partake of the promise...if they but trusted and obeyed...Helleluyah
To defeat death is the final "do JUST AS He did"...