A. I have not eaten it yet.
B. I have not yet eaten it.
1.Are these sentences grammatically correct?
2. Which sentence is "real talk" English.
It would be even more natural with the contraction: I haven't eaten it yet.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.
And of course, context! If you want to stress the 'yet', to indicate that you're going to some time, you'll probably use the version with 'yet' at the end - this isn't a hard-and-fast rule, but I think this sort of consideration affects our choice of where to put the 'yet'.