As to the origin of Codex Alexandrinus:
T. C. SKEAT, THE PROVENANCE OF THE CODEX ALEXANDRINUS,
The Journal of Theological Studies, Volume VI, Issue 2, 1 October 1955, Pages 233–235
Respecting a note in the manuscript thought to be by Athanasius II, Patriarch of Alexandria from 1276 to 1316,
"In the past it has generally, though illogically, been assumed that the note in
the Alexandrinus indicated that the manuscript had been in Alexandria
from time immemorial; but comparison with the Greek manuscripts
now shows precisely the opposite, viz. that the notes were inserted
because the manuscripts had not previously been in the Patriarchal
Library. Secondly, Athanasius's long absence in Constantinople makes
it highly probable that the Codex Alexandrinus, like the two Greek
manuscripts, was acquired by him in the capital. Whether all, or any,
of the three manuscripts were originally written in Constantinople is, of
course, another question; but if any future scholar wishes to claim a
Constantinopolitan origin for the Codex Alexandrinus, it is at least open
to him to do so. In short, Burkitt's conclusion may be right, though his
reasons were wrong. What is now virtually certain is that the manuscript
was carried from Constantinople to Alexandria between 1308 and 1316,
and that it remained in Alexandria until 1621, when Cyril Lucar removed
it once more to Constantinople, to present it, six years later, to
the King of England."