And Jill Came Tumblring After

WRONG

Trap Master can only be flipped during your turn or by the effect of another card. Since no card has been activated to trigger such an effect, Trap Master cannot be activated in response to Trap Stun.

The effect of Prediction Princess Tarotrei can flip trap monster face up on the opponents turn. 

Once we send that Prediction Princess Tarotrei to the graveyard, our trap sealing will stick around.

Ritual Sealing does not negate, only destroy. Prediction Princess Tarotrei is destroyed, but its effect is still carried out.

D.Va triggers her ult when there are no enemies nearby (why?) and Roadhog happens to come just after she triggers it but before it goes off, ignores all visual and audio cues that the mech is about to explode and pulls it?