User blog comment:Kaido King of the Beasts/Chapter 763: Another Backstory, Another D, and Another Great Chapter/@comment-24638955-20141008155950

This chapter explains so much about what happened. In a nutshell:

Cora/Roci helps Law hiding the secret of Law's "D" and Doffy will snap and kill cora upon noticing the fact of being hidden from his knowledge.

The Ope no mi will be found in underground trading.

Law will be able to use to use that definitive Skill from the Ope (He was seing studying a lot this chap) which means through the years (10?) continued to do so.

There's more but that just the same as reading the chapter.

Trivia: Rocinante was the name of the horse of Donquijote, It was and old horse that was very clumsy and tall.