I agree that your question is worded much more clearly than the one I linked to. If for no other reason than as a signpost, I'm willing to rescind my VTC, and move to a reopen :)
Why I called this a duplicate is that the two answers referenced combine exactly your answer your question.
1.) What variation exists? gets to the root of the "has it changed" question
2.) What is the lineage? gives you the resource to see exactly how the manuscripts differ, at the word-in-each-verse level.
Believe it or not, I think this was the first VTC I've ever done on a question of yours, and I promise it isn't out of malice. (I may often disagree with you, but as Monika says, I like your critical thinking.)
I still think this question covers existing ground, however.