Do I have to memorize all the status codes?
No, we do not need to memorize status codes, there are always resources with that information, just like the one we share in the exercise, although most likely, we will start remembering what does each code mean as we start using them often, at least the most common ones like
404 which is not found or
403 that means forbidden, usually in response to a request with permission credentials that are not allowed, or
502 bad gateway, that usually means the route has sent an invalid response, commonly related to an error on the server side.
Although it is always smart to bookmark or have a shortcut to the documentation of the codes.