a- The plane was targeted by separatist by mistake (as nor Russia or Pro-Russia separatist has anything to gain from
downing such a civilian plane) on the other hand I don't know how can the separatists can operate such equipment as it requires a minimum knowledge I guess
With what? Buk-M1 make too much radio signals with the radar, is easy to locate. No one located Buk-M1 inside Donetsk/Lugansk.