"Number Six is dead?" opinion/predictions

I know Number Six is Aihana Etsu and Aihana etsu is Spoilers but I really confused that time that where the f... is Number Six (Aihana Etsu) but then when I read a novel which is NT12.

I still confused why Kanou Shinka impersonating Number Six which is Aihana Etsu. But then I found a word that Aihana Etsu was just a "former" name. I don't why it becomes "former" and that word reminds that he is "dead?" (presumed.?) I don't why it becomes its former name. Maybe he/she just rename his name into the one we speculated for it or maybe he's been resurrected? But I just wanna know you guys to share your agreement or disagreement with this. But I stil don't know his background yet. (Sorry for the bad english)