THE CONSTITUTION OF THE REPUBLIC OF KENYA, 1963
Now it was officially recognized by the government of Britain the world in 1964, but in 1963, when they declared their independence , they considered themselves “The Republic of Kenya”.
If I’m not mistaken
You are mistaken, this has been debunked about 300 times today so you're in good company. The constitution you are citing is a 2008 modern amended one. The original one from 1963 does not refer to Kenya anywhere as a republic. In fact it recognizes the queen of england as the head of state, that's not a characteristic of a republic. There is a reason the kenyan's own official histories list the fact that they became a republic in december 1964 -- because they weren't one before!
See link to the 1963 constitution here:
http://www.constitutionnet.org/files/KEL63-002.pdf
