And your question about Bhisma deva, after he left this planet, he went to Vaikuntha. Because he was Narayana worshipper. In Bhisma's prayer, it is clear that he is worshipper of Four Handed Narayana. Although he knew that Narayana and Krishna are non-different, but his affection was for Narayana. Therefore he entered the Narayana loka.
Those who are devotees of Narayana or Krishna, they are not afraid of any planet, even they are sent in the heavenly planets or the hellish planets, because they have Narayana within their heart, they are equally situated.