You can't "hover" your finger in a mobile app.
There is no press effect markup because the way press is handled is natively taken care of. If you're using a button, the button itself comes with an inherent native press effect.
You could technically put a button at the top level but there's no point in doing so, because you can attach an action to items even if it's not a button. For example you could just do something like:
"text": "Press me",
This means each scrolling unit can have an action or an href at the top level.
But if you go down deeper, you must use buttons to attach actions.