> Earliest written records are from the Sasanid Empire.
I assume you mean the earliest records that document the name "Iran"? Written records of that region go back multiple thousands of years before the Sasanids.
I did find on Wikipedia at various points the claims that...
- The name "Persia" is just a misunderstanding of the provincial name Fars or Pars; the country has never thought of itself that way.
- The name Iran dates to the 3rd century AD.
Those two claims, both of which you seem to be repeating here, conflict in a pretty obvious way. The classical Greeks fought against and eventually conquered an empire they knew as "Persia", the Achaemenids, several hundred years before the Sasanids were established. Cultural contact between Greece and Persia was quite extensive, with many Greeks serving as mercenaries in Persian armies.
Wikipedia saw a big fight over the endonym of Achaemenid Persia -- the page went from noting it as "Parsa", rendered in Old Persian cuneiform, to claiming it was known by the modern Arabic name, rendered in modern Arabic -- a development at least a thousand years too late to be plausible -- to now recording "ch'shassa" ("the Empire"), again in Old Persian cuneiform.
The name Iran easily could go back long before the Sasanids, in that it represents a piece of culture shared with India and therefore presumably dating to before the Indo/Iranian split. But are you aware of any evidence that the country referred to itself that way during the classical period? Judging by what you can find on Wikipedia, this question is one of major political concern to some groups, and is mostly fought on the basis of assertion rather than evidence.