Google removed App Actions. BIIs like actions.intent.GET_THING do not work now.

What you can still do:

"Hey Google, open TestAppDemo” -> open app main screen.
If you want "groceries" screen -> need deep link or shortcut. Example: testappdemo://groceries.

But Google Assistant does not pass words like "groceries" to your app anymore. It only opens app or deep links.

So answer: No, you cannot do "Hey Google, open groceries from TestAppDemo" directly. Only deep link + shortcut workaround