Keyframes

I've had a couple of weird experiences when using keyframes in 2.40 - I
should note that I've fiddled a little with Blender in the past, but am by
no means an experienced user, so it's very possible that what I ran into
is something easily fixable.

I created a very simple scene - using the default scene and changing the
light to a spotlight.  I wanted to have the spotlight sweep over the cube.

I set a keyframe at frame 250 with the spotlight just covering the cube
from one side.  Then I set a keyframe at frame 1 with the spotlight at the
other extreme of the cube.  The sequence when I follow through
frame-by-frame was in the desired direction (sweeping "down").  When I
generated the animation, however, the sequence was reversed, and the light
swept "up".

I wondered if it might have to do with the order I added the keyframes, so
I went to delete them and set them back up again - only to find that I
couldn't figure out how to delete the keyframes.

My questions are these:

1.  Why did my animation flow backwards?  Was it because I entered they
keyframes from last to first rather than first to last?

2.  How do I delete a keyframe?

3.  On a related note, if I want to change the rotation point in the IPO
editor, is there a way to slide the rotation (for example) vertically?

Thanks,

Jim