Fully disabling dedicated graphic card

Will Nvidia graphics card be consuming power/generating heat after disabling it?

No

Will disabling the Nvidia graphics card driver in the Windows Device Manager fully disable it?

Yes

You can also override the default graphics processor for a program. You can activate a setting in the NVIDIA Control Panel that allows you to override the Optimus application profile setting and choose a particular graphics processor to use. To enable this setting, click View from the NVIDIA Control Panel menu bar and select Add "Run with graphics processor" Option to Context Menu. This setting will now allow you to right-click on any executable or shortcut and select the graphics processor to be used when running the application, either High-performance NVIDIA processor or Integrated graphics.¹

I've heard something about Nvidia Optimus technology. Is this technology applicable to this laptop?

Nvidia Optimus technology intelligently optimizes your laptop, providing the better graphics performance you need, when you need it, while extending battery life.

According to the official GeForce website the GeForce 840M GPU supports the Nvidia Optimus GPU switching technology. For laptops with GPUs that support Nvidia Optimus, Intel Core i3, i5 and i7 processors are supported.

¹_{How do I customize Optimus profiles and settings?}