I was a Hero Factory fan long before I was a real Bionicle fan, so I will try to answer these, though I bet Greg will do better.
I know you meant G2, so I'm not saying anything here. HF? Yeah, from what I've heard.
Oh, it was made by @IllustriousVar Industries. Okay, my guess is that it was supposed to do one thing but malfunctioned and became destructive, like IG-88 in Star Wars.
Toxic Reepa I believe was described as an alien... Maybe they wear armor or something. Saw-snake thing? Please link a picture, that sounds cool and I don't remember what you are talking about.
They are built and then enslaved by Mr. Makuro. Nah, I think they would have been hired.
Um... Now that's a good question... Maybe they weren't actually supposed to be kids? I don't even remember what you're talking about.
Is Vapor even canon? He's probably in some book, which I've never read. I would say maybe, obviously Lego just stuck on a recolored face.
Yeah, it's the same reason for an actor change for Lloyd. Oh wait, that one has a better reason than this does. I doubt it, probably just so Rocka doesn't have to assume the newbie plot point while being a member of Recon Team and facing up against Black Phantom.
Evo is probably for Evolve, Von Ness just don't worry about, he's Von Nebula for black hole, Fortis I don't even know who that is, and Rocka, well, my old friends and I theorized he was the earth type element or something. He is gold, and gold is a shiny rock. I don't know, find help for me please.
We'll never know... (eerie music)
Again, never read the books, but I assume it is just as bad a cliff hanger as Breakout, Invasion from Below, and Brain Attack. There were plans, I can tell ya.
I took Invasion from Below with a grain of salt, thinking it as more of a reboot, like G2, only lasting even shorter.
Plans? It's Herofactory, heroes don't need plans!
I can guarantee you, it's for easily recognizable imagery for ads and for the little ones. I mean, what is more fun than pretending to rip out the hearts of robots?
Steampunk. That's a joke, by the way.
Here's basically the best answer for every single question you just asked: It's Herofactory. They're selling the toys, not the story, but they give it a not-very-though-out story for the show and just to give something to play with.
You have taught me that I don't actually know everything about Herofactory. Thank you! I hope you find someone better to answer your questions... well, better!