Regarding the requirements for rewards level, stage 12 has roughly the same requirements as before; it’s randomly 10% higher for some reason but close. That must be why there’s a drop requirements for each of the reward 13 - 16. They had a planned total requirement for unlocking all rewards, but wanted to keep the requirement for stage 12 similar. That results in lower requirements for 13 - 16.
Of course, this isn’t addressing the change in weapon restrictions and new depends on the event troop/weapon.