Question: Why were Rob Riggle, Dave Franco, and Queen Latifah uncredited for their supporting roles?
Answer: Cameos usually go uncredited.
Question: After the final fight where Ghost is killed in the exploding helicopter, it is eventually revealed that he supposedly survived it during the end credits and returning for one of the mock sequels titled "34 Jump Street: Return of the Ghost." Did he really survive the explosion or was his return just a gag and he really died after all?
Answer: Given the obviously jokey nature of all the mock sequels in the closing credits and the highly explosive nature of what happens to him, it's probably best to assume that Ghost was indeed killed in the helicopter.
Chosen answer: While her fate is currently unknown, we do know that Brie Larson did not reprise her role for the sequel because of the story taking place in college.