Usable basement construction for kfw55 + wooden prefabricated house

Hello everyone, regarding the [Nutzkeller] I have now received different statements, some say you have to separate the cellar entrance with a wall and a door, others say you can leave the entrance open and only need to heat the cellar anteroom, and others say you don't need to heat it at all. What is correct here?

Thanks for your help

We have installed a stud wall with insulation in the basement anteroom. A vapor barrier was also installed on the exterior wall. The doors to the cold rooms have been executed in thermal class III. This anteroom is heated through the open staircase. This is the standard procedure of our developer.

When we inquired about the utility cellar, we were told that a door to the cellar is required because we are building KFW55.