The Imams عليه السلام do have the knowledge of what was and will be, and that nothing is unknown to them عليه السلام

5. Ali ibn Ibrahim has narrated from his father from Ali ibn Ma‘bad from Hisham ibn al-Hakam who has said the following. “I asked abu ‘Abdallah عليه السلام at Mina five hundred letters from al-Kalam (theology). I asked the Imam عليه السلام, “They say that he has said so and so.” Then he says, “You say so and so.” I then said to the Imam عليه السلام, “May Allah, take my soul in service for your cause, “This is lawful and that is not lawful. I know that you are the authority in this and you are the most knowledgeable person in it and this is al-Kalam.” The Imam عليه السلام said to me, “O poor, Hisham, Allah, the Most Holy, the Most High, does not require any duty from His creatures without first availing them all that they need to comply with the command.”