Very little - just colder.
It stops. It may break up or even volatilize.
It would get drawn, by gravity, into the sun and just get burnt up.
In that case, we die - all life on Earth dies. Life on Earth is completely dependent on the energy from the Sun.
-- If the line is straight through the center of the Earth, then it's the Earth's axis of rotation. -- If the line is marked on the Earth's surface and stops at both poles, then it's a meridian of longitude.
Then it would fall into the Sun. It is the Earth's movement (of about 30 km/second) that keeps it from falling INTO the Sun.
Tidal and tectonic activity will cease. Volcanic activity will increase and the earth will eventually look like Venus.
Nothing, the force of gravity is not affected by Earth's rotation. However measurement of WEIGHT would change.
If it stops there will be no life in earth.
deposition
It stops at about 0.12 seconds.
magnetosphere, its the magnetic lines of force generated by the moving magma inside the earth. It stops energized particles hitting the earth because a charged particle moving in a magnetic field creates a force perpendicular to the lines of force and the particle spirals down them to strike the earth at the poles. (the magnetic pole just happen to be near the rotational poles at this time) This all is the source of the northern (and southern) lights.
You die.