When you use water it acts as a bonding agent only. It has no effect on the outcome of the cake. If you use milk it adds an extra flavor and the milk carmelizes giving the cake a browner appearance.
Yes. Whenever I make a cake that calls for water, I always replace the water with milk. This makes for a more moist cake. You can add oil, but that can be tricky because you don't want to end up with an oily sheen on your cake. I would start by substituting milk for any water in the recipe, and see if you notice a difference.
Water can be substituted for milk with very little difference in the finished cake. You could also use reconstituted dry milk or canned evaporated milk thinned with water.
egg milk and flour
It depends on the cake and on the size of the cake. It is usually about one cup. But, just follow the recipe, it will tell you.
It shouldn't cause any problems. I have substituted soy milk for regular milk in many recipes without any problems. You usually can't even taste the difference.
2 cups in 1 pint.
yes you can'pretty much milk is milk no matter what it is labelled
Yes. It will be lower calorie, however it will not be as rich.
You can probably get away with it. I would add 1 teaspoon of oil for each cup. Water tends to produce more of a crust on baked goods than milk.
To turn the cake batter into a liquid. Why milk specifically? Because the recipe says so. I've definitely replaced milk with juice before and only good things have resulted, so I doubt that what you add really matters on a chemical level.
Yes, you can substitute evaporated milk for regular milk in a recipe, but you may need to adjust the consistency of the recipe by adding water to the evaporated milk to reach the desired thickness.
To substitute evaporated milk for regular milk in a recipe, use an equal amount of evaporated milk and dilute it with an equal amount of water. For example, if the recipe calls for 1 cup of milk, you can use 1/2 cup of evaporated milk and 1/2 cup of water.