These are my opinions, so don't take this as fact. Take from it what you will.
1) Fantasy uses a force, power, relic, or other such unexplainable phenomenon in our world yet is given either a vague or understood explanation (magic, for example, would be a force). Science fiction uses technologies that don't exist, could exist, or do exist yet places them in a setting that questions mankind's progress and use of technology, often revealing a philosophical question of sorts and expresses either a dominating human spirit or our collective insignificance (Humans are Special or Humans are Bastards).
2) The target groups for either fantasy or science fiction tends to be around the young adult ages (teenagers to mid-20 year olds), though both genres can appeal to a broad spectrum of ages.
3) Fantasy tends to be dismissed or clumped with High Fantasy, e.g. Lord of the Rings, while science fiction has a greater hold on Western societies. This could stem from the cultural icons that are Star Trek and Star Wars, among many others of course.
4) Fantasy as a concept could be argued to be as old as humanity since many of our earliest stories are of gods creating the world to epic heroes and myths that explain the world in a grandiose way. Science fiction, however, could be traced to the famous authors H.G. Wells and Jules Verne due to their fantastical stories of traveling below the surface of the earth and oceans, wars and exploration is space, and even traveling through time.
5) Both are popular genres across the industrial and post-industrial world, offering a sense of escapism and bringing dreams or fantasies to life. They allow us to see the world through a different lens, be it the hope of change or the hopelessness of humanity.
I hope I answered your questions to your satisfaction.
