When did 'arya' become 'aryan' ?

'Arya' is a term denoting good conduct and cultured behaviour in the
R.gveda.

When did the term, 'aryan' as a linguistic category evolve -- a
categorisation which rapidly degraded into a people category?

Accordingto Labov (1994: 27), 'The close examination of the present
shows that much of the past is still with us. The study of history
benefits from the continuityof the past as well as from analogies
with the present." [Labov, William, 1994, Principles of Linguistic
Change, Volume I: Internal Factors. Language in Society 20 Oxford
UK, Blackwell.]

When did Sarasvats become Hravats? Earlier than the times of the
Behistun inscription which mention the latter category of people?