1) Can't really answer this; I've only ridden clipless.
2) Shimano SPD m520 - great beginner clipless setup. Mountain >> road for walking (for example, I don't use extra shoes for grocery runs, only have a pair at work for the dress code).
3) m520s are double-sided, so I would venture a guess that it would actually be easier to clip in than having to flip the cages.

I don't trackstand, and starting and stopping is fine for me in my urban environment.