Okay, here’s the basic-est way to explain it.

Y’know the portals that the kids get sent through as babies when they’re riding the meteors?  The scratch changes where those portals go and rewrites history to accommodate that change.

Their exact sections haven’t been determined in-comic but the cover of the Sburb music album does provide some idea. 

They traveled to the Furthest Ring which is the area between sessions. 

It’s common for Space players to wake up on their moons before the session begins. What causes someone’s dream self to wake up varies from person to person. 

Here is a list of songs used in-comic. 

The Beta kid’s guardians aren’t related. 

She has that too, how else would she be able to use personality?

Maybe but accourding to Nannasprite she just disappeared one day so I think it’s more likely that she left. But who knows.

That did happen with Roxy and Dirk.  In that case they could use the teleporters on Prospit and Derse to get back to Earth.  The Derse duo ended up entering with Jake.  How other players would pull that off is unknown, they’d probably have to hitch a ride home.

No, it was necessary. Dirk’s dreamself was knocked out at the time and the kiss woke him up.