It takes an hour for all 72 layers of protection between the Royal Palace and the Seiretei to seal back up.
Gigi is not limited to her Immortality and using her blood to take over people. She can also use corpses to rebuild the lost flesh of others.
The entire attack on the Seiretei was a feint to leave the path to the Soul King open. Squad Zero played right into Yhwach's hands.
Orihime and Chad arrive from Hueco Mundo.