dtgreene: Wizardry 2 requires you to import characters from Wizardry 1, and they keep their level (in fact, you need a character with level 7 mage spells to get past the first level).
kbnrylaec: Wizardry 2(original version) was basically an expansion pack or DLC of the first game, in today's term.
Later released version includes a pregenerated party and the ability to create new characters.
That is, the re-released Wizardry 2 become a standalone game.
Most of the versions released for consoles (specifically the versions made by ASCII corporation) are actually a remix of the scenario which differs from the original in many ways. The maps are different (but many of the original features can still be found somewhere), the game is balanced so that new characters can get somewhere, and there are monsters from Wizardries 1, 3, and 4 in the game. Stat caps are now racial minimum + 10 instead of 18. Some spells had their level adjusted (DIAL is 3rd level in stead of 4th, for example), and there are a few new spells (LADALTO). Monster stats (including those of bosses) have pretty much remained the same, however.
Also note that the ASCII version was released in Japan under the title "Wizardry 3: Knight of Diamonds", as Wizardry 3 was previously released for the Famicom as Wizardry 2. I note that the Famicom version of 3 didn't see an English version, so the English NES version of Wizardry 2 (which, remember, is a remix of the original scenario) was released under its proper number.
The PSX version is a special case, as it is based on the original version rather than the ASCII version. You can create characters, but they start at level 1, which is too low to survive; the pre-made characters start at level 10. Fortunately, that version contains 1, 2, and 3 on the same disk, making transfer between scenarios easy.
DrLove: As for exploits, in DM there were a few generators, which spawned screamers and the worms, which you could kill for food. Even later in the game, when everything else was cleared, it was trivial to go back to the rooms to restock on food if needed. Back when I was young and stupid, I thought about going through the entire game without the extra food, but now that I'm old and stupid I think I have better things to do.
I've never seen that as an exploit. In fact, I think the first screamer generator was put there intentionally so that players could get more food and practice if needed.
Incidentally, Chaos Strikes Back has a worm generator really early in the game; it happens if you stand on a square that is notable for another reason (hint: if you've played the game, you've been on that square). With that said, getting back to that room is *not* trivial; the dungeon design isn't that friendly.