Lord Chaitanya: Appearance of Lord Chaitanya

                                                                  Q. 1. I have read in the Krishna Book that in the 31st cycle of the Vaivasvata Manu, the Dvapara-yuga changes places with Treta-yuga due to the appearance of Lord Krishna. I would like to know how Krishna appears in the other cycles of other Manus.

                                                                  Q. 1. I'm confused on the subject of yuga avatars in this cycle of Kali. Gaudiya Vaisnavas claim Sri Caitanya Mahaprabhu as the avatar for this particular cycle of Kali yuga. Since he has already appeared, will this kali yuga end without the appearance of the Kalki avatar? This seems to contradict the Vishnu Purana.