What will be the CLI command to check the irule against a virtual server specific for a particular customer ?

And, you can do:

show ltm virtual XYZ-HTTP detail

It will give you stats about the iRule like this (you will have to scroll down a bit):

  ---------------------------------------------------
  | Ltm::Rule Event: Webtop_intercept:CLIENT_ACCEPTED
  ---------------------------------------------------
  | Priority                 500
  | Executions
  |   Total                  120
  |   Failures                 0
  |   Aborts                   0
  | CPU Cycles on Executing
  |   Average                  0
  |   Maximum                  0
  |   Minimum                  0

  ------------------------------------------------
  | Ltm::Rule Event: Webtop_intercept:HTTP_REQUEST
  ------------------------------------------------
  | Priority                 500
  | Executions
  |   Total                    1
  |   Failures                 0
  |   Aborts                   0
  | CPU Cycles on Executing
  |   Average                  0
  |   Maximum                  0
  |   Minimum                  0