This is the step to disable the shutdown/restart/suspend/hibernate options in the start menu.
(1) Open the Local Group Policy Editor by Start > Run > Enter gpedit.msc
(2) Go to User Configuration > Administrative Templates/ Start Menu and Taskbar
(3) Enable “Remove and prevent access to the Shut Down, Restart, Sleep, and Hibernate commands”
But How to add some RDP user to allow reboot, here is the step
(1) Log in with administrative rights
(2) Start > Run > Enter secpol.msc (Security Policy Editor).
(3) Go to Local Policy > User Right Assignment
(4) Locate the “Shut down the system” , you can see the user that have privilege on it. Just right click > properties , then you can add the user on it.