I just picked up the wand of magi and get the free spell trap casts, I also use spell immunity but am wondering does spell trap stop EVERY type of spell, also does spell immunity include within it every type of spell immunity?For instance is spell trap going to stop imprisonment? or spell activated through stepping on traps? I am not too convinced that say spell immunity evocation stops a fireball trap from damaging me, or is that classed purely as elemental damage?

Also, how does the invisibility work? If I'm invisible and cast protection magic I seem to be able to be targetted sometimes, I was watching a walkththrough on youtube a while back and I'm sure they said invisibility is only broken when using magic that affects other characters (albeit my cover could have been blown by resist fear). But this brings in to question the invisibility of the wand of magi, as it gives you invisibility and you attack you lose invisibility, is invisibility restored by switching to a second weapon and switching back for instance?

The other thing is when using project image, I think the image is dispelled by an enemy using true sight? Does immunity abjuration prevent the dispelling on the prjected image? does the projected image have to use abjuration or the caster if it does?

Spell Immunity makes you immune to all (or almost all) spells of that school. If your projected image casts Spell Immunity: Abjuration, the image, I believe, can't be dispelled with Dispel Magic, but can still be dispelled with True Seeing/Sight; if you want to protect against those spells, have the image cast Spell Immunity: Divination. (Spell Immunity: Divination is also useful in conjunction with Mirror Image or the various forms of invisibility.)

Spell Immunity: Evocation will protect you from Fireball (as will (Minor) Globe of Invulnerability), but there is a catch: If you are not playing the EE, it (and similar protections) will not protect you from your own spells. Hence, casting Spell Immunity: Evocation, charging into a group of enemies, and then casting Fireball on yourself is going to result in you taking damage from the fire (unless you avoid it with something like Mirror Image (yes, it works against Fireball) or Protection from Fire). Note that the EE changes this behavior, allowing spells of this type to protect against your own spells.

I believe the various spell protection removers are not affected by Spell Immunity.

Effects like Spell Immunity do work against traps, provided the trap is affected by a spell.

Melf's Minute Meteors is an interesting case: Each meteor has two effects, one of which is physical damage (which can be blocked by Stoneskin), and the other of which is a separate 3rd level Evocation spell for each missile (meaning that it can be deflected, turned, or trapped, but each missile will use up some of the capacity). That makes the spell great for dealing with enemy protection spells, with the exception of Protection from Magical Weapons (and with the caveat that, if an enemy casts Spell Trap, you will be restoring the enemy's low level (up to 3rd) spells).

Here's one other case to consider that works differently depending on whether you are playing original BG2 or the Enhanced Edition: Contingent Skull Trap on caster.

Original: When the effect triggers, the game will see that the spell is targeting the caster, which, for whatever reason, makes it ignore magic resistance entirely. Hence, magic resistant enemies will always be affected, despite their magic resistance. However, you will not be able to defend against it with SI: Evocation or (Minor) Globe of Invulnerability, making it not that easy to take advantage of this quirk. (Note that this also affects Sunfire, but that spell gives you 100% fire resistance for 3 seconds so that it doesn't damage you.)

EE: The spell does not ignore magic resistance, so it's not quite as good a strategy here. However, your own SI: Evocation or (Minor) Globe of Invulnerability will work here.

Anyway, I suggest testing some of this out yourself, using the console to cheat if needed. Remember that the targeting protection that Invisibility grants also applies to targeted spells cast by allies, so you can take advantage of that fact to tell whether it's possible to target a character with the spell. My favorite places for testing are right outside Watcher's Keep and at the start of Throne of Bhaal (before meeting the first enemy of the expansion), as those places allow you to rest freely (unlike towns, for some reason) and don't have enemy spawns to mess up your resting.

yes the staff of magi re-enables invis on re-equip