Is the Hajj and 'Umrah accepted if the pilgrim throws the jamarāt all at once due to severe crowding, and is Hajj required to be repeated?

Throwing the pebbles all at once is considered as throwing only one pebble. The one who threw in this manner, and whoever deputized him, must slaughter a sheep to be distributed among the poor of the Haram for each person, while the Hajj remains valid.