If the sun were to suddenly disappear, the Earth would experience immediate darkness, as sunlight takes about eight minutes to reach us. Without the sun’s gravitational pull, the planets, including Earth, would drift off into space in a straight line. Temperatures would plummet, leading to a collapse of ecosystems and a rapid decline in life as we know it. Ultimately, the planet would become a frozen, lifeless world.
Sun
corona
If ozone layer disappears, UV rays will enter the earth. these are fatal radiations of the sun.
The sun is hidden by the earth. It's why the sun disappears at sunset and reappears at sunrise.
Yes, but according to the bible when it disappears we will not need it.
Solar eclipse or blocked by clouds
metamorphosis
It will be impossible for life to exist without the sun. In fact, even before the sun totally disappears, life on earth will be gone. Check this website : http://www.dlr.de/en/desktopdefault.aspx/tabid-1/86_read-18304/
Sunset time is the moment when the sun disappears below the horizon, typically occurring in the evening.
Dusk
If by "disappears" you mean ends its life cycle then, no, you wont be able to see the Moon. Mostly because by the time the Sun is gone the Earth would have been swallowed long ago and we would all be dead!
The time when the sun disappears below the horizon at the end of the day is known as sunset. This marks the transition from day to night as the sun's light is no longer directly visible from the surface of the Earth.