1) Dunno. I would presume so, though.
2) Sometimes. I'd use fresh veggies to supplement their algae, instead. (Your Betta might like it, too)
3) NOT PETCO! (I just don't like Petco. They are horrible when it comes to Betta treatment). Petsmart is actually probably a pretty good idea. I have yet to find one from Petsmart that's actually a Chinese Algae Eater (this is apparently a widespread problem).
4) No, but they would like one, or some other hiding place. They'd also like a little chunk of
driftwood. Not necessary, though. My two surviving otos are in a tank with no wood.
5) Not an issue. Their primary source of food is the algae on every surface of the tank. They will latch on to fresh vegetables that provide them a relatively stable surface.
6) Not sure, but otos are fast little buggers when threatened. Miyamoto tried to eat the otos for a couple of weeks after I added them, but they'd just outrun him. Pretty soon, they learned where they were safe when the koi was around. (That's right, folks, even the tiniest of fish has more than a 3 second memory)
7) Nope. They largely don't care about other fish. They just care about sucking up algae.
8) They're river fish, and like some current. As long as you've got a good filter that's turned all the way up, they should be okay.
No worries about the number of questions. That's why we're all here.