Jade is John’s sister genetically. Nanna was with the both of them through the three years so of course she interacted with Jade.

She changed clothes and helped the blind Sollux up to the roof

The Alpha kids’ Jack was the one that was in jail, Caliborn’s Jack helped him with the Eight Ball planet and then Caliborn killed him, or at least he said he was going to

They’re staying in the dreambubbles.

Players can use their classpect abilities before ascending seen by John,Terezi, Rose, and others. Going God Tier only strengthens their abilities and allows them to be honed further.

There was something that either activated the abilities or transformed her into the undead. It’s possible that it was caused by being exposed to the Witch of Life’s blood or that her corpse was kissed by a Blood player or that she just needed to die in order for her latent abilities to come to fruition. We just don’t know.

It says them in the narrative on the page when they enter their lands as well as other times throughout the story

Gamzee is just a terrible person, he didn’t “go insane” he’s just awful and was acting even worse than usual because he was pissed off that Aranea was mind controlling him.

There’s a page on the wiki detailing all it’s appearances

That is the Prankster’s Gambit, it’s a meter that raises and lowers depending on whether the person pranks or is pranked.