So for the modern translations, are they pronounced exactly as "Never Fear" in greek or are they "They Never Fear" ??
Not sure what you mean by "pronounced." Like all other languages, Greek distinguishes (and has always distinguished) between the imperative (e.g. "never fear") and the indicative (e.g. "they never fear").
Also, was attic greek the language most used by ancient athenians during a certain time period with other dialects being integrated? What time period was this?
The Attic dialect developed from at least the 11th century BCE and lasted into the Roman period. It was spoken in Attica, a region in east central mainland Greece which included the capital, Athens. Eventually, like most other Greek dialects, it yielded to the "common" Greek that came to be spoken throughout Greece, Asia Minor, and the Middle East after Alexander's conquests. However, that "common" dialect was itself heavily influenced by Attic Greek.