MB4 231b: What Type of Grain and Using a Whole Loaf for the Eruv Chatzeiros (366:6-8)

For an eruv chatzerot bread is required unlike שיתוף מבואות which can be other food. The bread has to be whole loaves not slices. What if part of the loaf is lost?

The practice of collecting flour from the residents and making it into one loaf.

What if people give different types of bread?

One person accepting the eruv on behalf of everyone else

Using bread made from rice, lentils, or other grains.