September 2017

I'm a bit confused, the credits and Snapchat show humans and trolls living on Earth c but in Calliope and caliborn's back story, it showed alternia. Did the trolls just happen to find a planet identical to their home? Also does it matter the the father cherub destroyed alteria c as well?

It didn’t show Alternia, it showed a planet populated with Trolls that the Cali twins’ father attacked. When their mother caught up to him they fought and she won. He then slithered off and laid an egg on far off future Earth.

Where/how did we learn that Earth C is where Caliborn and Calliope were born? (I never caught that and suddenly hearing this makes me scared for the epilogue)

We first get the idea when we see a shitty statue of liberty outside their meteor and we get confirmation in a convo Caliborn has with Hussie shortly after entering

We know that in the end, Vriska shoves LE into a black using a juju the kids were sucked into. Assuming they were able to pop put the other side, would it then be possible to find the destroyed Earth C, and, combining Jake's Hope powers (he would probably have advanced a lot, because all that time on Earth C is enough for growth as a person), Dave's time powers, Jades' space powers, etc, and reclaim/reinhabit the planet? Or am I overlooking something?

They could just travel back to the time they were living in, several billions of years in the past. The Earth at the point in time when they fight Caliborn is in his Medium so I doubt they’d want to stay there