TestRunListener.beforeStep eventHandler is not triggering TestStep execution

Not at pc.
Open groovy script and look the editor's right corner of title bar.
You would notice context, log, test runner etc.,
Similarly you can notice wherever one can script such as the events, teardown, setup script for test case, suite, project etc.,

So one can only use those variables in that script. Other than those will lead to error. That's the reason if some script works in test step, but not in the event in your case.