1) BCIs are
boa constrictor imperator such as Colombians, Nics, Hog Islands, Mexican, and other Island boas. BCCs are boa constrictor constrictor such as Peruvians, Surinames, Guyanas, Brazilians, etc. BCCs usually get larger than BCIs and these are the "true" red tails; when someone calls their Hog Island or Colombian a "red tail boa" it's not correct IMO.
2) I've personally purchased from Jimi Snakes, Boamaster, Chad Duggin, and Dan Eby with success.
3) I've read that Central American boas are more hissy pissy as babies but have no first hand experience with this. My three Colombians are amazingly tame, much tamer than my Hog Island (though I think she's a fluke as most Hogs are well mannered).
4) Male BCIs usually will need at least a four foot vivarium/cage, females will most likely need at least a 6'. I keep my boas a little cooler than my balls and it seems they prefer the cooler temps. Don't feed baby boas more than once a week and I feed my adults every 2 weeks.
See my collection HERE