The arm rests front only flips down if you push the button. But it doesnt totally go down or forth or back. But it also depends on your seat position.
The voice button has more use then siri alone. Siri is long press. But the car it self has voice help to which is for different things.
I think it is difficult when buying new to tick all the options because it adds up quite easily. But doing things afterwards is mostly even more expensive. But you can retrofit armrest as far as i know.