To remove power options from the Start menu, you’re going to need Windows 10 Pro and launch group policies to restrict access to them.
An administrator account is required. To launch group policies, just click the Start menu and type Edit group policy. Navigate to the following path:
User configuration > Administrative Templates > Start Menu and Taskbar
In the right pane, look for an option called Remove and prevent access to the Shut Down, Restart, Sleep, and Hibernate commands. Double-click it to open its settings.
By default, this option is set to Not Configured, but in order to disable the power options in the Start menu, you need to enable it. Simply check the option that reads enabled and then close the window.
As the policy itself explains, enabling it also removes the power options from the Windows Security screen launched with CTRL + Alt + Delete. On the other hand, third-party apps could still be able to reboot your computer, so have this in mind when enabling the policy.
Needless to say, if you want to return to the original configuration, edit the policy once again and change its status to Not configured or Disabled. A reboot isn’t required.
If the policy is active, clicking the Start menu and trying to access power controls is blocked with an error reading There are currently no power options available. Pressing Alt + F4 on the desktop is also blocked with a message reading This operation has been canceled due to restrictions in effect on this computer. Please contact your system administrator.