If anyone, any guru, who has some false ego that he is guru, but really he wants money, wealth, reputation, some position and is running after them to be happy, then he is not guru. He may know so many śāstra quotations, but we should offer praṇāma to him from very far away...

Why is Janmastami not called Madhava-tithi? Why are Gaura-tithi or other holy days not called Madhava-tithi?...

Gaudiya Vaisnavas observe all visnu-tattva appearance days along with special fasting. Sometimes these days come next to each other or next to an Ekadasi or Dvadasi tithi which is meant for fasting. This happens every year somewhere in the world for Lord Varaha Dvadasi and Lord Nityananda Trayodasi, but not at all locations due to different sunrise times.