About last episode, since Regulas’ abilities are poorly explained in the anime.
Regulus can remove causality from anything, when he does this, the object in question continues to move as if in a complete vacuum of space time. That’s how he killed Reinhard, he literally threw air without a time axis at him. An object can’t change if time is not applied to it, so everything else around it must change to accommodate it.
Regulas can blink and the air it displaces will become deadly. That’s what he did to immobilize Rem and disarm Crushe.
The water and sand is the same thing. He killed Pandora by throwing sand without time at her.
Only reason Reinhard’s sword didn’t get deleted when hit is because it’s a weapon crafted by the gods that need not obey the laws of the universe. But he sent Reinhard flying at a constant rate, the time axis removed, hence why he seemed to float across the screen.