[casualcryptic]

Actually, there are usable versions of the divine beasts, but only Obelisk sees play because the other two are too expensive tribute-wise for their abilities.

And I can answer that question about TCG vs OCG as well. It stands for Trading Card Game vs Original Card Game I believe and the distinction is that yugioh was originally made by two companies which put out cards side-by-side. The cards could be used interchangeably but certain cards only came in packs produced by one company or the other. Interesting, no? Anyway, they both held separate tournaments. OCG allows... pretty much everything. And regular TCG rules do as well, but most tournaments and the Duel Networks rating system work off of the TCG advanced system in which certain cards are limited or banned.

So in short, when you hear TCG vs. OCG it usually refers to card restrictions vs. anything goes.