5/ You can attach a script to character, items, and so on in D:OS2 engine. Then on this script, you can call events, like on use, on equip, and so on. But you don't have those nice usefull simple slots, only one script.
However, I am currently working on this,
for example:
http://larian.com/forums/ubbthreads.php?ubb=showflat&Number=620653&gonew=1#UNREAD and some effects require osiris to function.
Overall, I find D:OS2 engine, so far, to be more limited and bulkier, as far as scripting is concerned, than The aurora toolset. However, keep also in mind that I am only getting used to it. But I miss the NWN2 way to do stuff...