Nothing
Same as today...yeast flour and water
It reacts with the sugars to make it rise.
Yeast doughs are used to make countless types of bread. "Dishes" made with yeast dough would be pizza and calzone.
Pretzels are made with yeast dough. Cake yeast could be substituted for dry yeast, or one might make a "sponge" or sour dough starter which uses wild yeasts from the air. But some sort of yeast must be used in order to make actual pretzels.
To allow the dough to rise so you get a lighter, less dense end product.
If a yeast dough is not rising, there really is no good way to fix it. Try again with fresh yeast or a different recipe. If the problem is that the dough has been placed in the refrigerator, and the dough is not rising there, it is either too cold, or it has not been left to rise long enough. Remove the dough from the refrigerator to a warm place free from drafts. If the yeast is still viable, the dough should rise in about two hours.
Cake is made from batter not dough, which does not contain yeast, it does however expand when baking.
No you cant use yeast to make rice but you can use it to make bread i think. Who would use yeast when making rice? Yes, you can use yeast in a similar manner with rice flour as you do with flour that's made from wheat.
Adding salt to bread dough controls the action of the yeast and improves the flavor. Bread made without salt will have a coarser texture and a blander flavor than bread made with salt.
biscuit can't be made without maida flour, because it is high in protein than atta. gluten is the protein and it is important to make the dough. Though it is low in fiber contain than atta flour , it gives crispness to the biscuit and also be stored for long term than atta flour.
Yeast is made up of microorganisms (fungi) that feed on starches and sugar, producing gas that makes dough rise. Yeast can digest sugar quicker than starches, so rises faster when sugar is included.
Batters and dough made with baking powder are ready to cook as soon as the ingredients are combined. Baking powder dough does not require time to rise as yeast dough does.