Do you have to cook cabbage before you freeze it? ALSO, how do you freeze potatoes without them turning black

If you freeze raw cabbage, it will not be the same when you defrost it.

Freezing most leafy vegetables kills their structure. There is a lot of water in the cabbage's cells. Once it freezes, it breaks the cell membrane and will wilt upon thawing.

So, yes - if you must freeze your cabbage, cook it first.

As for potatoes, why do you want to freeze them? If you keep them in a cool, dry, dark place, they'll last for weeks. If you must freeze them, then cook them first. Again, though, this will not do great things to their structure and they'll likely be powdery once you defrost them.

All vegetables must be at least blanched prior to freezing. The potatoes will turn black if they are peeled and not cooked immediately. So either cook or blanche your cabbage and completely cook the potatoes. I just don't understand why you are trying to freeze potatoes. Store them in a cool, dry, dark place and they will keep for quite a while. If you have a garden and are expecting a bumper crop, then a root cellar would come in handy.