The upside will take care of itself. Yes, this is a simplification, but you must start with this thinking. A good read through the TurtleTrader site will offer more detail. A. No, because they keep changing. Think about it.
Markets are the same because they always change.
The key is to trade a system that responds to change. But, if you have a basic philosophy that's sound, you can take advantage of those changes to make money by capturing the bulk of a trend. It is the same with using good, sound business principles, the changing world is not going to materially hurt you if your principles are designed to adapt. This is precisely why Turtle trading has continued to work for all these years. These techniques are designed to predict the future which can't be done.