Yes, white girls can have black hair. *insert confused smiley here*

As the other poster mentioned, on DARK hair -- anything beyond dark blonde, really, you'll only get a highlight. The brightness of the highlight will decrease as the depth of color increases.

If you don't re-bleach the new growth, and just touch it up, you will still experience the same effect: the new growth will be barely a highlight, whereas re-coloring the bleached part will reinstate the brightness. What I'm saying is that you will have a noticeable demarcation between bleached and unbleached as your hair grows, even if you keep touching up with the Manic Panic.

Bleaching always causes some damage, but it's not typically irreparable. Careful treatment, lots of protein followed by moisture, should mitigate the damage but no, you will never escape all damage when bleaching hair -- it's just the way bleach works.

If you get a proper bleach kit -- not a blonde hair color kit -- you will should only have to bleach virgin hair once to get it light enough to take a bright color. If you want to maintain the brightness of the streaks, you will have to bleach the new growth before applying the color. Otherwise, like I said, you'll only get a highlight.