The Existence Of God And Modern Laws And Government
I think that both of those questions are adequately answered in the link that I shared above. You might want to go through the videos and the text again. In short, God contacted human beings (prophets and messengers) to remind us of our test, to give glad tidings to those who have accepted the truth and are preparing for the hereafter, and to warn those about life in the hereafter and the Day of Judgement who are oblivious to the fact.