Sanctions can't do shit against Iran just like it was ineffective against Russia which is the most sanctioned country on earth.
Iran gets all of its stuff from China and Russia via rail or caspian sea.
The blockade is a game of chicken and I know Trump is going to blink first. China could well keep Iran afloat with credit and then own Iran like they do it in Africa and others with a debt trap. Just like they own mining rights in many countries they could get hold of some of Iran's oil well until there debt is paid off.