What is the true significance of prasadi (sacred remnants of food or clothing, etc. from a Saint or Deity)?
Uddhava, the close friend of Shri Krishna, is probably the most qualified person to realise the importance of prasadi. Uddhava was one of the greatest jnanis of his time. In fact, Shri Krishna had said that His friend was no less than Himself. Uddhava was a complete renunciate, a complete jnani and a complete premi of lover of God in all respects. He declares in the Bhagavatam that no amount of spiritual knowledge, penance or devotional practice is enough to free the soul from the clutches of maya. In this respect, Saint Tulsidas says in the Ramayana, "Even great personalities such as Sage Narada Ji, Brahma, Vishnu and Shankara cannot overpower maya." In the Gita, Shri Krishna Himself issues a challenge, "O Arjuna! Only the one who surrenders to Me completely can rid himself of maya with My mercy and grace."
No amount of devotional practice can liberate anyone from the clutches of maya. Maya is so powerful. But Uddhava, the great devotee, issues a challenge in the Bhagavatam (11.6.46) by declaring with confidence that we can defeat maya by using His remnants - be it food, clothing, ornaments or anything else that has been touched, used or eaten by Shri Krishna. In comparison, devotees who perform severe penances or some other austere devotional practice using their own faculties and strength, all fail miserably. Uddhava clarifies further that among these various types of remnants, eating Shri Krishna's leftovers as prasad has the maximum impact overcoming maya.
Is it certain that those who have regularly been attending your satsang will be reborn as a human being?
All over India only those who are regular and committed participants in our satsang try to practice rupadhyana, and sometimes even shed tears in loving remembrance of God. This makes an impression among people - and rightly so - that they are sure to be reborn as human beings. However, if someone succeeds in surrendering completely to God, then he is sure to go to Golok.
If a seeker leaves his mortal body during the course of his devotional practice, who will be his guru in his next life?
The Guru who is his guardian in this lifetime will continue to guide him in his next birth. Alternatively, some other Guru can take care of him at the behest of his present day Guru.
Original answers given in Hindi by Jagadguru Shri Kripalu Ji Maharaj