How do I check if the running instance of WB is Batch or Interactive Mode?

You can use the Boolean ExtAPI.UserInterface.IsBatchMode

Example:

import clr
clr.AddReference("Ansys.ACT.Core")
import Ansys.ACT.Core
 
AppAPI = Ansys.ACT.Core.ApplicationRepository.GetApplication("Project")
ExtAPI = AppAPI.GetExtensionApi(None)
 
is_batch_mode = ExtAPI.UserInterface.IsBatchMode
 
if is_batch_mode:
    print "Batch MODE"
else:
    print "Interactive MODE"