Yes
Yes. You would need to configure settings>system>input>peripherals>CEC to allow for this and just have your remote keymapped to a CEC suspend function. The default mapping for the OSMC remotes will turn turn on a TV by pressing the home button 2-3 times, and will send CEC suspend if you hold down (long-press) the home button while the home screen is active. It is possible to make the suspend work this way on any screen with a user customized keymap tweak.