Group competition rewards do not get sent to your inbox. To collect group competition rewards, you need to open the group rewards screen when the competition is finished.
If you do not collect your rewards and take part in another competition, the rewards from the current competition will replace the previous rewards when the current competition finishes, and you won’t be able to collect them.
If you do not collect your rewards and take part in another competition, the rewards from the current competition will replace the previous rewards when the current competition finishes, and you won’t be able to collect them.