What did the Prophet, may God’s prayers and peace be upon him, see in Paradise and Hell on the night of the Isra and Mi'raj, and was that a revelation or a reality of what he witnessed of those being tormented and those being blessed, knowing that there is no one in either of them now?

Paradise and Hell exist currently and will not perish. The Prophet, peace and blessings be upon him, saw them on more than one occasion, and his vision was a real vision. Scholars differed regarding the nature of this vision; some held that it was a real physical sight, while others believed it was a vision of the heart or knowledge. However, the first opinion is the most probable and closer to correctness.