Can I Do Any Of These (Item Questions)

Before I start a map I want to make I better make sure I can make this map. It revolves entirely around certain items, so here it goes:

1) Can I make it so that a character's ability forces him to sacrifice an item and the result depends on the item sacrificed.

2) If #1 is not possible, is having a usable item without the number in quantity number visible possible? These items are supposed to require a slot each and if you have a duplicate I want to make sure they can't be stacked. Plus I just don't want the little number in there.

3) I want all the items that the game revolves around to be of their own category (for the sake of my triggers), is that what the "Unknown" category is for? Can somebody explain what the entire "Unknown" category is there for?

4) This one isn't as big a deal since I doubt I'll be doing this, but if you guys can answer me I'd be really grateful. Say your character has the basic functions (Move, Attack, etc.), and all of his special abilities come from items? Is this possible? If you don't get me, think of the character with just the basic commands. He picks up an item, and Invisibility pops up where the abilities usually go.

Thanks all.

1 ,2,4 are possable with trigging .making your own catagure for an item is hard coded I think unknowed is debug fuction I think .

for number 1...
items cant be stacked.. i thought u knew that, and lets say fer example, staff of teleportation, its not-perishable and it does something,

for number 4...
take the cloak of shadow, and modify its ABILITY,

You can by using a back pack like system it uses lots of triggers thou.