Well, you made that pretty complicated. I assume by reading your answer, that there isn't any fruaudulent returns and that I filed everything on time and do not expect to amend any of them, 3 years is the right answer.
Didn't understand this comment though, don't know what those numbers referred to:
"You owe additional tax and situations (2), (3), and (4), below, do not apply to you; keep records for 3 years"
You didn't answer the question:
What is (2, (3) and (4) refer to.