
In his first life, did he also have the ability to see other's stats?

Well, for mc, I don't think they ever mention how he dies, in the novel, the last thing mentioned about his past is that he made some sort of bet with Lucifer about Hyungsung. For the ml, Atlanta or that god, basically sacrifices themselves to send him to the next timeline. It's a bit complicated and i believe i too haven't fully understood about the bet.
About the masked trash, it is Kiyoung, currently he only has half of his memory, later in the novel, he gets his full memory about the past timeline and also crazy thing, the past him talks with his current self or atleast once refers to himself in future tense.
The ml finds out about mc being masked trash from a guy he will fight in future, and well, he pretty much loses his mind and 'kills' Kiyoung in anger. But yea he immediately regrets it since the current timeline Kiyoung is his everything and he tries sacrificing himself for Kiyoung. So while he is a bit angry, his love (not romantic way) for Kiyoung kinda dismisses it. I think Kiyoung also apologies in his 'final moments'.
This was such a good moment during the novel haha
Woah Konohamaru is a savage (⊙…⊙ )