Regarding your questions, “I read in a book sent from India that Srila Bhaktivinode Thakura was sent directly by Lord Sri Caitanya from the spiritual sky. I am not sure if the book was bona fide. Is the above true? Someone, a God-brother brought up that he heard that Srila Bhaktivinode was at one time an impersonalist. Was he ever?” Yes, what you have heard is all right. Just like Arjuna is constant companion of Krishna, as it is confirmed in the 4th chapter, Krishna says that both Arjuna and He appeared many times on this world, but he had forgotten his past appearance and Krishna did not. Krishna is like the sun, and maya is just like darkness. Where Krishna is present there cannot be any darkness of maya. So as Arjuna although always in the presence of Krishna as eternal companion in friendship, still he had some illusion in the battlefield of Kuruksetra, and Krishna had to dissipate that darkness by the teachings of Bhagavad-gita. The purport is, sometimes even a liberated person like Arjuna plays the part of a conditioned soul in order to play some important part. Similarly, Bhaktivinode Thakura for sometimes was associating with the impersonalists. And then he exhibited himself in his true color as pure devotee, exactly in the same way as Arjuna exhibited in the beginning as a conditioned soul, and then as a liberated soul. So there is nothing to be misunderstood in this connection. Krishna and His devotees sometimes play like that, as much as Lord Buddha although an incarnation of Krishna, preached the philosophy of voidism. These things are conducted in terms of place, audience, time, etc. In the Caitanya Caritamrta it is said that the activities of the Vaisnava cannot be understood even by the greatest scholar. So we have to understand everything through the transparent via media of the Spiritual Master. So there is no doubt about it that Srila Bhaktivinode Thakura is eternal energy of Lord Sri Krishna Caitanya Mahaprabhu. And whatever he did, was just to suit the time, place, circumstances, and etc. There is no contradiction in his activities. Yes, also, what you have learned about Sukadeva is correct. He stayed in the womb of his mother for 16 years because he was fixed on the Brahman conception, and then on hearing the Srimad-Bhagavatam, he became realized and decided to come out and be active in the service of the Lord, to enjoy blissful varieties.
From Srila Prabhupada’s letter to: Madhusudana — Los Angeles 20 November, 1968