Giga Guess and Doomsday's answers combined would be correct. I'll let the two of you fight over who gets to ask next.

---EDIT---
Trine is missable if you don't get it in Great Glacier and/or if you beat Godo before getting the fourth, and final E. Skill materia.
Pandora's Box is used by Dragon Zombie only once in the entire game, so if you don't learn it that one time, then you never will (and you can double up E. Skills to one character for them to both recieve it).