Option 1 -> Nagaland became a separate state in 1963, carved out of Assam, but was never known as NEFA.
Option 2 -> Arunachal Pradesh was officially called the North-East Frontier Agency (NEFA) until 1972, when it was renamed and made a Union Territory.
Option 3 -> Assam has retained its name throughout history and is the parent state from which several northeastern states were carved out.
Option 4 -> Mizoram was part of Assam as the Mizo Hills District and later became a Union Territory in 1972, but was not called NEFA.
Hence, Arunachal Pradesh -> NEFA was renamed as Arunachal Pradesh in 1972 when it became a Union Territory, and later achieved full statehood in 1987 -> correct