You got rewards based on your achievements. If you earned up to III, you get I, II and III.
I is a joke ef. Mostly just a lulz item to have for lulz.
II is a moderately powerful ef - it has the stats of candy +4, with +50 luck. Probably the best item to have of the three if you're looking for all around power.
III is untradeable, and a top of the line ef. It even has in the description, "Congratulations, PvP Master." It is leaned more towards transformation, most useable by rams, or top tier surge pvpers who use trans to its full extent.
And yes, thanks for noticing I misspelled it BVv2. I did that every time for all three, I can't type BCv2 for some reason. I thought I corrected it.