Hi Jawadh,
Your server needs either ArcGIS for Server Advanced edition or ArcGIS for Server Standard edition + the ArcGIS 3D Analyst for Server extension.
I'm not sure I understand the second bullet:
- Do GeoProcessing on flat vectors like and create extrusion in the web scenes...?
If you are using tools in the 3D Analyst Tools toolbox to create 3D features in either ArcGIS Pro or ArcMap, you will need the ArcGIS 3D Analyst extension.
Joanne