The responses:
- all new item instances will create a new handle. Even it the new item is added to an existing stack, it will have created a new one temporarily
- both cases in treasure use up handles in the same way. -1 is guaranteed to give you what you ask, while 1,1 may fail to find level-appropriate items and you won't get anything
- if by incomplete objects, they mean scenery, yes those use handles as well, but they come from a different pool. Sceneries are objects which are purely decoration though. So as soon as you can to interact with it, or reason about in scripting, it will be an item. Globals can never be scenery, as scripting can reason about them.
- characters, items, scenery, triggers all get their handles from different pools. Handles never change for existing instances, but each time you spawn (by script/skills/...) a new instance, a new handle will be created.
