[karlosovic]

1. jaheira is an elf and so she is multi-class. Imoen is human so she can only dual-class. multi-classes advance in both classes and have their Exp split between the 2 (or 3). Humans can only dual-class which means they start off in 1 class, then *change* to a new class. the old class is inactive until the new one gets to a level of 1 level higher than the 1st class. then the 1st class re-activates, but only the new class can ever advance again.

This means with Imoen, say you dualed at level 3 to a mage. her thief class disappears for a while until you get to mage level 4. at this point she gets back her skills from the thief class, but all new exp goes onto her mage from then on.

2. dunno

3. people can identify items based on their Lore skill (see the character sheet in-game-the head icon (4th icon on side of screen?)).
Bards have the highest lore, then mages and thieves, everyone else is pretty low. The higher the characters lore skill, the better the equipment they can identify without using a scroll or spell. crossbow bolts are harder to identify than say, arrows of the same enchantment.
ps. lore is also effected by wisdom and intelligence. check your manual for tables in the back