Responses

1. Because of Adrian.
2. Because Agni was an obstacle for Adrian's plans. Remember that Agni was gifted by the goddess. That's why it'll be a problem if he prepared the fight with the killer.
3. Dunno, maybe Kyle. ┑( ̄Д  ̄)┍
4. Undertaker's role is to make Realciel the heir once and for all. And maybe it was Vincent's dying wish.
5. Probably, since he's found out RealCiels corpse is alive and kicking. But maybe he's a double agent. Everything bound to happen with plot twists so yeah.
They’re giving us all the background without actually answering the most pressing questions like:
Why is real Ciel alive?
Why did he kill Agni?
What is the younger twin’s name?
What is the Undertaker’s role in this?
Is Tanaka now on real Ciel’s side?