” . . . in the end of the three synoptic gospels: . . . “
So what you are saying is that you believe that when Christ spoke of teaching to “observe all things whatsoever” He commanded (Matt. 28:20), he pulled a curtain between Matthew 27 and Matthew 28, and He abrogated everything He had commanded prior to Matthew 28. It is as if everything else He commande up to that point was disannulled.
What “curtain”?
The curtain you, in affect, have drawn, so that Christ’s commandments to His disciples in the Synoptic Gospels only applies to what He said in the last four verses of Matthew.
All things whatsoever He commanded includes all of His commandments He ever made to them throughout His earthly ministry, all the way back to chapter 4.
And my point is, NOT ONE SINGLE organization on earth today professing to be a Christian church teaches anybody to observe ALL things whatsoever Christ commanded — NO Catholic church, NO Protestant church, NO Baptist church, NO “Christian” church of any name or description.