The trolls stopped pestering Dave and Rose because after John died that timeline became a doomed timeline and the trolls could only see the alpha timeline in Trollian so they couldn’t contact them anymore.

In the stories that Jade and Jane told to Calliope in the last intermission.

Yes

FLARP was a roleplay game played by Team Charge (Aradia and Tavros) and Team Scourge (Vriska and Terezi).  Vriska took the game too far and controlled Tavros into jumping off a cliff which paralyzed him.  To get back at Vriska, Aradia summons the ghosts of all the trolls Vriska has feed to her lusus to haunt her.  In retaliation Vriska controls Sollux and forces him to kill Aradia.  Terezi, in trying to get justicecontacted Doc Scratch to tell him that Vriska had one of his cue balls.  Doc Scratch then made the cue ball explode making Vriska lose her left arm and eye.  In revenge Vriska mind controls Tavros, making him use his psychic powers to control Terezi’s unhatched lusus into telling Terezi to go outside and look into the Alternian sun which then blinded her.

No because original timeline John and Roxy will arrive in the retcon timeline when Homestuck starts updating again.

Retcon Timeline Roxy is dead.  Heiress Jane threw her stabby stick at Rose and Roxy jumped in front of it and died a heroic death. 

It’s the timeline where Aranea never came back to life, Vriska wasn’t killed, and Terezi never entered an abusive relationship with Gamzee.

Yes

Twice   Canonically

I’m afraid that Complacency of the Learned is not a real book so there is no place to read it.