u/-Freude

I've never seen Star Wars, I'm interested in buying Fallen Order and Jedi Survivor which are on sale.

Part 1, Chapter 12, ended with 9S transferring his consciousness into a mechanical unit, but in Part 2, Chapters 1 and 2, he's seen in his original form. How did that happen? Why were there remains of 9S in the desert if he was still alive? Why does 2B kill him after interacting with the talking head?