[Lal]

@Johnny_Lim:
“A Deva-born-Sakadagami will attain Nibbana faster than a Brahma-born-Anāgāmi, right?”.

There are few things that need to be taken into account in your whole analysis:

1. A Sakadagami will not come back to the kama loka once born in the deva loka. But he MAY attain the Anagami stage, and be born in the brahma realm before attaining Nibbana.
2. In the case of Anagami, he may not need to spend the whole maximum possible lifetime for that realm before attaining Nibbana. He may attain Nibbana shortly after being born there; nothing to prevent that.
3. Same kind of arguments for one who attains Sotapanna stage in the human realm. Those remaining seven bhava could be in any higher realms, depending on when he/she attains Sakadagami or Anagami stages.