My guess would be that osmotic concentration of the sugar gets so great that the yeast is unable to get enough water for growth.
Directly regulated by sugar and salt. Sugar cuases yeast growth, salt slows. Environmental factors such as moisture, heat and acidity also affect yeast growth.
Yes.
temperature (30 degrees celcius is the optimum temp for yeast growth), nutrients (e.g. sucrose, fructose, glucose, lactose - (does not affect yeast growth), pH level (5 - 6 is the optimum pH level for growth)
Yeast can use oxygen to release the energy from sugar (like you can) in the process called respiration. So, the more sugar there is, the more active the yeast will be and the faster its growth (up to a certain point - even yeast cannot grow in very strong sugar - such as honey).
Temperature of its environment, amount of sugar, type of sugar, and acidity.
Yes, because the yeast feeds on sugar. Fermentation cannot continue if there is not sugar as the yeast will not be able to convert it to alcohol and carbon dioxide.
Yes.
Letting a water, sugar, and yeast mixture ferment for a long time does not affect the quantity of ethanol produced.
Temperature, oxygen availability, pH, sugar concentration.
Moisture, warmth, energy(sugar)
No and go get a life
This is actually not a chemical reaction. Yeast are living organisms and they use sugar as an energy source, so if you put yeast and sugar together the yeast will consume the sugar and give off carbon dioxide. This is why breads made with yeast rise and have small holes in the bread after it is baked - the holes are where small bubbles of carbon dioxide were trapped.