“I remembered there’s two stories that I have come across where a Frog after it got killed, was birthed into the Deva realms and another story of some bats were able birth into the Deva realms due to some monks chanting in the cave. Can we say that in those two stories, the animals were at the end of their Bhava?”
– It may be possible for those things to happen even if they had not reached the end of the bhava. But those are VERY rare.
– When the gandhabba comes out of the body at death, if the causes and conditions line up, it is possible that it may grasp a new bhava.
– Workings of the kamma, in fine detail, can only be done by a Buddha.
“There’s also a Jataka story of the Bodhisattva being in hell.”
I don’t think that is right.
– The lowest realm a Bodhisatta can be reborn is the animal realm. Even there, The animal cannot be smaller than a certain size.
“..how much meritorious deeds we had to do just to get a human birth?”
An alternative way to look at this could be helpful.
– We all are likely to ALREADY (in previous lives) have done kamma to be born in the lower realms as well as higher realms.
– One could be mindfully engaged in punna (kusala) kamma and avoid papa (akusala) kamma to be able to grasp a “good kamma seed” rather than a bad one.
– But the only way to guarantee that a bad seed will not be grasped is to get to at least the Sotapanna Anugami stage. That is by comprehending the Four Noble Truths/Tilakkhana/Paticca Samuppada..