July 2015

Is the reason Sollux talked with a lisp that he had 2x as many teeth as normal, which is why his lisp went away when he fell down the stairs and got them knocked out?

Probably, having messed up teeth can cause a lii2p

Can one planet have more than one Sburb session going on at the same time? Like are the official Kids the only earthlings playing the game, or are there other sessions?

There are others

Why did Terezi and Vriska kill all those troll children during their FLARPING days, and were Eridan and Feferi involved in this too or something?

Vriska killed them to feed her lusus. Eridan may have been involved since he used to Flarp too but Feferi most likely not involved.