Is there a way in Revit to identify left and right columns which are supporting a beam ? . I want to know exactly which one is from left side and which one is from right side.
Right and left is relative... Revit understand as 'End' 0 and 1 (start and end).
For a given element (e.g. beam) you can get all connected elements (e.g. column) with:
ICollection<ElementId> columnIds = JoinGeometryUtils.GetJoinedElements(doc, beamElement)