Photosynthetic cells contain chlorophyll and other light-sensitive pigments that capture solar energy. In the presence of carbon dioxide, such cells are able to convert this solar energy into energy-rich organic molecules, such as glucose.
Yes, you can add a little lemon juice or vinegar to the goat's milk to make it into a buttermilk or kefir. This will lower the pH of the milk, and allow it to release the CO2 stored in the sodium bicarbonate (baking soda), causing the bread to rise. Goat's milk generally has less fat and more vitamins.
Yes, you can make liquid whey and kefir cheese instead of cream cheese/liquid whey if you like. Just use kefir instead of clabbered milk. Adding the kefir grains to the clabbered milk is fine if you want to do it that way. The kefir cheese might turn out a bit strong tasting though ..