There is one heating control by the steps leading upstairs. The stairs
area is heated by a radiator that cannot be turned off by hand. I notice
though that there is a place on the radiator to use a key. I presume
then that I can turn this radiator off using a key.

I only want to heat up one room. I want to place the heating control in
that room. Is it then okay that I just shut of that radiator by the
steps with a key? I presume it is, but just checking.