How do I provide internet access only to a single Android app? I am currently using Android Smartphone. 
I am currently having internet access for my Android Smartphone.
I would like to provide internet access to only a single android application, for example: WhatsApp.
I do understand that I need to provide internet access to some essential default system apps for the functioning of the phone.
Is it possible to selectively provide internet access to few apps and not for other apps?
Try Opera Max to restrict per app data access to mobile and Wi-Fi networks. The PlayStore description says it,


  
  Block apps &amp; prevent data leakage:
  Control your apps’ internet usage by blocking apps from running in the background that are using mobile data or Wi-Fi without
  permission.Blocking apps running in the background conserves battery and minimises your battery usage.
  


If you want to restrict only a particular app follow the steps,


Open Settings menu > Data Usage
Select the app you want to restrict the data.
And select "Restrict background data"


If you are on a Wi-Fi network and you want to restrict the app accessing data in the background using your wi-fi connection, do the above steps in the Wi-Fi Tab to restrict the app access to Wi-Fi network too.