Demo servers are fully featured Traccar instances. You can send commands to real devices.
Note that SMS service is obviously not available, but you can use normal data-based commands.
I understand, I was looking for an endpoint that would show me the commands that have been executed on a device, doesn't it exist?
No.
I would like to know if with the test servers it is possible to send a command to a real device to turn off the engine of a car. If something is missing, what would it be?