I have A STM32 Nucleo l4r5zi.
It is placed somewhere and I have only control over the PC who the Nucleo is connected to.
I want the Nucleo to stop supply 5v out from his pin IN ANY WAY.
I don't care to restart the nucleo or shut it down. just somehow stop for a 10 second the supply power from his 5v pinout.
How can I do this ? I tried to solve it from the OS (by stoping supply the USB with power) but i could not manage to do so.
I can only change the code or change things on the os. no any physical modification
As the schematics prove, you cannot reprogram the "main" STM32 controller (in your case, STM32L4R5ZI) to switch off the '+5V' signal.
Instead, you have to reprogram the ST-Link controller on the nucleo board (STM32F103CBT6) so that it controls pin PB15. Note that this will probably render your nucleo board useless (apart from the use not to drive the 5V pin...). I'm not aware how simple it is to reprogram the ST-Link controller. If this really is what you want to achieve, you should post another question if/how an arbitrary firmware can be flashed on nucleo's st-link controller.
Of course, you can remove the jumper JP6, but as I understand your question, you don't have physical access to the board.
If by "on the os", you mean to change the configuration of the USB port on some PC attached to the board, this question appears to me to be off-topic, so I don't follow this path any further here.