1a. No.
2a. I don't think so.
3a.
Quote Originally Posted by AZn2th3N's Item List, GameFAQs.com
Level 4 Key Sphere
Usage- unlocks level 4 lock
Steal- Nemesis (Monster Arena)
S. Rare- N/A
Drop- Seymour Flux (Mt. Gagazet)
- Spectral Keeper (Yevon Dome)
- Omega Weapon (Omega Ruins)
D. Rare- Land Worm (Inside Sin)
Bribe- Chimera Brain (Calm Lands)
1b. You have to complete all the training excercises, then do the Chocobo Catcher race for the Sun Sigil/Caladbolg.
2b. Nope.
3b. Yes. Loading the game and leaving the screen also resets the number of dodges.
4b. You won't have to fight DY unless you go to the back of the cave, and the DMS's summoners can be avoided if you approach from the Djose Highroad.
5b. Keep trying.
6b. http://www.gamefaqs.com/console/ps2/game/197344.html
7b. You should have been in 450 battles by the time you reach the Calm Lands. If you're hunting for Dark Aeons and Celestial Weapons I think it is safe to assume you have been in more than 450 battles.