Though we've tried our best to cover everything you need to know in the guides and data sections, there are a few things which didn't fit neatly into them, or aren't particularly easy to search for in their sections. Such information ends up here, in the FAQ.
Have we missed something important? Let us know by adding your FAQ suggestion (preferably along with an answer) to the pinned FAQ topic in the Final Fantasy IX forum.
For your own good, we've put some of the more sensitive FAQs behind a spoiler wall. Make sure you have spoilers turned on to see everything.
Save The Queen and 
Hammer?There are really just two primary versions of the game out in the wild: the original PlayStation release that was also released as virtual content on PlayStation Network, and the newer version that was optimized for mobile devices and later released for Steam. The newer version allows the user to turn on a number of cheats to make the game easier, for folks who want to play for the plot and not grind through the entire game for 40 hours or more. Beyond that, the differences are primarily in the interface and in higher-resolution textures where available; there are surely some minor bugfixes and dialogue changes as well but nothing of real note. You can use CoN's guides for any version without issue.
A pretty cool dude, but whether he's really friendly or not is up for debate. For more detail, see the CoN forums.
The Cotton Robe Trick is a money-collecting venture that exploits an awkwardly-chosen set of gil values on certain items to make lots of gil early-ish in the game. To execute it, you need to collect 
Wrists and 
Steepled Hats and synthesize them into 
Cotton Robes. You can then sell the robes to make a profit of 630 gil per.
You can use 
Tents in battle, which is a bit strange. They heal the target. But the trick is that they also, for some reason, add some status debuffs if the target isn't immune to it, so it can be used to quickly cripple particular enemies.
The typical answer for this is Popos Heights, above the exit to Gizmaluke's Grotto. Outside the forest there are Grand Dragons, which can be dispatched with Quina's Lv5 Death. Definitely have that ability, as otherwise it's a tough fight for most of the game. They also give 3 AP, which is a good value for a non-boss monster. Adamantoise, Gigan Octopus and Whale Zombie are also good overworld monsters for 3 AP and can be found near each other, but not until later in the game.
Yes, if you're careful. See our the walkthrough, chapter 1.6.
There are three: Zidane's Thievery, powered by stealing; Freya's Dragon's Crest, powered by the number of dragons the party has killed, and Quina's Frog Drop, powered by the number of frogs caught in all marshes.
Save The Queen and Hammer?With the former, nothing. It's just there to have. For the latter, you can synth it, or you can hang onto it to see some very minor changes to the game's ending.
As best as it's ever explained, Ozma appears to be a lost Eidolon. Its location is clearly described as an Eidolon cave.
You might think there would or should be, but no. Just the usual intermittent, unintended goofy comedy in some dialogues based on whatever awkward name she has.