1. Actually the sensor is 14.5 Mp, but it uses 12 Mp. The extra pxels are used to avoid cropping in different aspect modes. See Gordon's review.
2. The camera has the seme modes as a DSLR so, with some limitations, you can do all those things. You can't blur the background like a DSLR with a fast lens does, because the sensor is so small, the field of view is quite large at the distance and focal lenth you use for a portrait, but you can have decent blur with good light and a relatively distant background. You can surely do the "dreamy water" effect ( I personally don't like it, water loses it's transparency and highlits/sparks that make it to look like water, it looks like wool to me-but this effect is so commonly accepted that I feel like wistling in church when I express my opinion
)or the panning thing with the fast mooving subjects.
3. I'm afraid that it's not possible. Although the camera has a slower zoom when in video mode in order to minimize motor sound, in relatively quiet scenes you can still hear it.
Canon PowerShot S100
Canon 50D , SIGMA 10-20 f3.5 ,Canon EF 24-105 L IS USM, Canon EF 100/2.8 macro Canon EF 50/1.4 ,Canon EF 85 f1.8,Canon EF-S17-85 4-5.6 Old Tamron 28-300 inherited from my Canon Rebel G film camera