How do I get view's group by in COM API just as that of M:\Sample Vault\1. Documents\By Class

Do you want to get the folder contents? Or get the actual view definition? 

what I mean is the grouping level settings as it is done as shown in the image

If you know the view ID then you can get the view definition using GetView: M-Files API - GetView Method

The view contains details about the "Levels", which is the grouping definitions are referred to in the API.

Yes, I know the view id but now I want the grouping and when I try to pull levels on some it shows 0 when I try a count. The main reason for this is because I have a view without name, so I wanted to pull grouping as the View name instead as shown in the attached image.

On some views it will return zero, depending upon the view definition.

The screenshot you gave for view 184 doesn't have any groupings defined, for example, so I would expect it to return zero.