I was curious about point 3; was lion air responsible for detecting the failed AOA sensor or someone else?

I can't exactly say but a quick read comes up with some relevant points:

"According to the reports presented to the Indonesian parliament, a Florida-based aerospace company performed the repair of the faulty AOA sensor."

https://airlinerwatch.com/broken-aoa-sensor-in-lion-air-737-... [from april 2019]

So possibly it's not LA's fault, however

"On Nov. 5, CNN published an update on the crash investigation from Capt. Nurcahyo Utomo of Indonesia's National Transportation Safety Committee (KNKT) noting that the FDR review also concluded that the aircraft's airspeed indicator had been malfunctioning on four consecutive flights prior to the crash. Utomo also indicated the pilots should have recognized the malfunction when it occurred on flight JT610."

https://www.aviationtoday.com/2018/11/07/faa-issues-boeing-7... [from nov 2018]