I'm new to threadless stems, and even after a lot of googling I have some qeustions:

1. No Locknut. On my threaded headset, I'd adjust the play with the big nut and locknut. My understanding is that on the threadless system, this is done with the small hex bolt. Since there's no locknut, how is it that this stays put?

2. Loosened Top Nut. I removed the top nut and even took the top cap off, yet the adjustment of the headset stayed the same (that is, it didn't get loose). Is there something that needs to be tapped?

3. Stem above tube. On the used bike I just bought, the top edge of the stem is slightly above the steerer tube. Is that the way it's supposed to be? Should I fix that?

Thanks!