How did the Prophet, peace and blessings be upon him, come to know the signs of the Hour and so on, and did Allah inform him of them, bearing in mind that he did not speak concerning religion of his own accord?

All matters of the unseen about which the Messenger, peace and blessings of Allah be upon him, informed were through revelation from Allah Almighty. Therefore, he must be believed in everything he conveyed. Whoever disbelieves him in even one matter that has been authentically reported from him apostatizes from Islam.