Stilling playing around with FF4Kster and a few other programs. I figured I should hold off on asking questions until I have a decent amount of them, but I think we've gotten there now, so...
Oh you bright eyed yearner of wisdom, learn now the sadness and the tragedy of Slickproductions and the vast amounts of knowledge lost to the dusts of time.
Alright, enough with the dramatics. It's great to see someone who has so many ambitious ideas for FFIV, I'll try to give my thoughts and possibilities on accomplishing each of them.
1) Changing world map - How does the game know when to bury Mist, open up the passage around Agart and re-close it? Has anyone played around with this? Is it possible to expand on this feature in the game? (Like say, having an area go from forest to desert after an event?) Best I can tell, it's related to the game flags, but that's as far as I've been able to figure out.
There is a flag which tells the game that Mist Events have occurred, along with the Agart mountain hole, but you've likely figured that out. I do recall that Chillyfeez had found information relating to the placement of tiles through flag manipulation, but I don't recall what it was he discovered.
2) Item depletion - how does the game know to not remove the Crystal (that Cecil uses in the final battle) from inventory? Is it possible to extend that to another item (or preferably multiple ones, like some of the event triggering items?)
Quite an intriguing question. The game treats the Crystal as a "Key Item" the same way it treats the Legend Sword. However it is unlikely it can be applied to anything outside the usable Battle Items because the game doesn't know what graphics and effects to draw for items that have been used in that way. Here's a test you can try... in FF4kster try to change the "Key Item" of Crystal in the "Features" tab to something else like... Cure1, and see if Cure1's are used up any more.
3) Is it possible to alter the battle commands and what they point to? Specifically, I'm wondering if Edge's Ninja magic can be redirected to draw on a Call magic list instead of Black magic.
The listing is purely superficial. Edge's Spellbook can contain whatever spells you want in them without there being any real issue, as far as I'm aware. Ah, unless you mean you want him to link into Rydia's Call magic...? I'm a little confused what you are looking to accomplish here, admittedly.
4) Sprites - An idea I had (probably several lessons in assembly hacking away from being able to do this, but still) was to re-direct Golbez' battle sprites to use the three sprites of Anna's so he could have a complete sprite set, then just using a monster slot for Anna. Is this possible? On that same note, is it possible to re-direct the game to look to either the toad portrait or the mini-map sprite for Golbez so he's not spread across three different characters?
A great question... I know nothing about that, but that is an interesting idea. Were it up to me, I would scrap the Pig spell entirely against PC's and just use it as the base to put Golbez in the game without replacing any characters, but ideally we could expand the rom... but again, outside of my purview of knowledge.
5) The ship - I get there's no spot to tell the game what the ship should do with the various map tiles (can pass, not pass, etc) but I keep seeing in various hacking notes that there's spots in the RAM to track the map tile you're currently on and the adjacent ones. Would it be possible to manually insert parameters for the ship so when the game detects there's, say, a mountain next to the ship it won't let you move there? Or if there's a walkable terrain to disembark the ship?
It's possible, sure. the best example to look at would be the Enterprise in the Underworld for the brief minute that it can't cross Lava, if you can figure that out you might be able to program the ship to act in that manner. As for disembarking... you might be able to use a normal event that occurs when you touch the water tile next to a dock or what have you.
6) FFIV's config menu - you can load your savegame up with an FF4 rom, use the config (such as changing the button inputs) and then load it back into the FF2 rom and the settings will stay, so is it possible to just re-insert the FF4 custom menu into the FF2 rom?p
I think someone's actually done that or has tried to do that, but I can't distinctly recall...
7) Jumping hero - Looking through hacking notes, I noticed NPCs have an option to spin jump and make forward jumps, which are blank for the player sprite. Would it be possible to link the blank command to the code for jumping to make the hero jump? Following on that, assign the command to a button for a jump function like in Final Fantasy: Mystic Quest?
All characters have the ability to jump in the air, we see them do it several times in cutscenes throughout the game. I can't see it as anything but automated though, FF4 is very stringent with where you are at a given point, jumping from layer 1 to layer 2 or things like that would be incredibly difficult to set up.
Successive world map triggers on same co-ordinates - specifically, I'm wondering if you could have a pre-bombed Damcyan that changes to the standard ruined Damcyan after the Red Wings bomb it. Is it possible to have a trigger change where it teleports you depending on what flags are on?
There are indeed! In fact, this is how the hallway before the Baron Throne Room works. Unfortunately FF4kster never made it to the point where you could edit triggers on the Overworld, if you could you would be able to take one of the unused Tower of Babil Overworld entrance tiles and set it to trigger an event sequence that searches for an enabled or disabled flag, and proceeds accordingly. It can be done manually with a little hacking, using old surviving notes (at least I hope they survive...).
9) Underworld expansion - The game has the same area available for the underworld as the overworld, but half the data slots? What would it take to get the same amount of data slots for the Underworld?
I'm not sure what you mean by data slots... care to elaborate? If you mean increase its size, that shouldn't be difficult. You can easily add one or two new areas to it by using Yousei's old editor and attaching the right trigger data to it.
10) Chocobos - I saw somewhere on here some info on getting the Yellow Chocobos to stay put when you dismount them which I would like to try to implement, but can you do the same for Black chocobos? Another idea I had was making Rydia's Chocobo summon useable on the map and having it call a chocobo to the party's position. Possible? Also, is there a way to make chocobos able to enter locations like Boco does in FF5?
Not without some major hacking... the game doesn't remember where the Yellow Chocobo's are, it does with Black Chocobos. It might be easily possible to kill the "return home" part of the Black Chocobo code, therefore allowing you to keep it. FFIV is very picky with sprite allotment in maps. You could pretty easily create a sequence that shows a Chocobo running the player through a given area, but you couldn't allow the player to have control during it.
11) Rydia's Magic orbs - Something I'm hoping to do is change the magic lists to something closer to FFV where the entire party shares a white magic and black magic list instead of having individual lists for each character. Obviously this doesn't work with the learning magic at level up system, so I'm wondering if the way the magic orbs add spells to lists could be adapted into some sort of a spell shop system?
My first FFIV hacks were looking into how the Summon Orbs worked... (and yet that data was never entered into FF4kster... *sniffle*) If every character has the same magic list you might be able to cannabalize alot (And I mean A Lot) of items to make a spell shop system, so... you might want to think of another way. An easier way is to use events to do this. Though it is innately hacky... Say you want to have each town sell three black/white spells. You could make a couple items called a "(Orb)Spell" of varying levels. You could have a White Mage NPC activate an event asking the player. "Do you want to use a Spell Page to inscribe the Mute Spell or..." YES/NO. If yes, search for a Spell Page, then the player gains the Mute Spell. If you choose No... "do you want the Shell Spell or..." Rinse and repeat. It's hacky... but it accomplishes a similar system, IF you link all the magic systems together... or you can code your own spell learning system using the shop ui as a base... but I wouldn't know how to go about that.
12) Shadow party - I still would love to know how Chillyfeez figured out how to keep everyone in the shadow party, instead of having multiple Kain and Tellah actors. Also, does Golbez have an actor?
Thanks in advance.
Only Chillyfeez can really tell you that. Golbez does not have a proper actor, no. As you noted his functionality is basically split. The NPC for Golbez does not correspond in battle with Golbez. With some hacking it might be able to be done, along with changing his class to Lunarian or something, but as you noted he is lacking some frames...