According to Quran (just like Bible) God has always been and always will be. Time, and its concept depends on our own ability and the way we have accepted it or use it in our lives.
As for your second question, again according to Quran God created human to “worship” him. But this word worship is usually taken on face value. Its not like one should just sit on an isolated island and cut him off from the world and just keep on worshipping God the way he believes. Islamic meaning of worship is that human should live the way God wants them to live, not only for themselves , but also for their neighbours, for society and for this whole humankind as well as each and everything (known or unknown to him them) should benefit from their actions.
In the end, human will never know about everything and it is a fact. We human are trying to find about other planets but we still do not know perhaps more than 50% of our own planet.