What foods can and cannot be frozen?

Many foods can be frozen and later thawed with no problem. Dairy products are not so easy. I can freeze my cheese but not the plastic cups with sour cream it. I don't really need to know what can be frozen, I need to know what cannot be frozen. I live where some foods are difficult to get (such as sour cream) and only travel to where it is available (about 300 kilometers away) about once a year. And what needs to be defrosted first in the refrigerator rather than right away at room temperature?