1. All Hellenic factions (at least in Hellas proper) can get Spartiatai, this includes the Koinon, Epeiros and Makedonia. But the only way for the last two is through adoption. In one fo my former Makedonian campaigns, I got a guy who had the "Spartiates" as well as "Completed Spartan Agoge" trait through marriage.
2. No idea

Maion