okay...here is my question what is least in the kingdom?
There is no such thing as "least in the kingdom". Your reference is to this:
"Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven" Matt. 5:19
The author is using the figure Synoeceiosis, or Cohabitation. The repetition of the same word in the same sentence with an extended meaning.
"Syn'-oe-cei-o'-sis from "sun", together with, and "oikeiosis", dwelling in the same house.
This figure is so called because two words are used, and in the general sense, but with a different and more extended signification. They dwell together as it were in the same house; and yet, while one speaker takes up the word and uses it in the same sense, he yet means a different thing."
The Latins called it Cohabitatio, cohabitation, a dwelling together.
In the former place, the allusion is to the distinction which the Pharisees made between different commandments (think of the Catholic distinction between 'venial' and 'mortal' sins).
There is no such distinction, and therefore, when in the latter place Christ says "he shall be called least," he means that he will not be there at all, for there will be no such distinction there. There is no least in either case.
the “you have heard it said” or the “but I say...” .
Here again, you are probably conflating what the Pharisees taught through the Oral tradition which is necessarily heard rather than what is written in the book of Moses. Note that every time Jesus says anything referring to what is heard, or said, he isn't referring to the Mosaic law at all. Every time he is referring to the Mosaic law, he will explicitly state that fact, e.g. 'Haven't you READ what it says in the book of Moses...etc."
The Pharisees kept the Sabbath but didn’t enter into His Rest and prevented others from entering into His rest?
Christ kept the Sabbath as well. Keeping God's commandments is NOT what allows one to enter into the kingdom. Keeping the commandments is NOT what saves anyone. Just because one keeps all of the commandments doesn't then mean they are saved. Two can be keeping God's commandments;" one will be taken, one will be left."
One keeps the commandments because they are created for good works. They are begotten from above as a new creation in Christ. The other must rely upon their own "will and effort"( Romans 9:16) which will never be enough to save anyone.
This isn't to say that they shouldn't keep God's commandments because all of God's commandments are created for the benefit of all humanity, regardless of whether one is saved or not. They are not meant to save anyone. They are what the saved believer does.
It is only the carnal mind, or the carnal man who can never be under the law because the carnal mind or man is of the flesh while the law is spiritual.(see Romans 8 for more)