Explanation:

Atmospheric refraction cause bending of light gradually producing a curved path. This causes the sun to remain visible to our eyes for several minutes after it has set below horizon. Thus atmospheric refraction tends to lengthen the day.
Elliptical appearance of sun near the horizon is the result of atmospheric refraction this happens because rays from the lower edge of the sun are bent more than those from the upper edge.
We see a blue sky due to the phenomenon of scattering of light.

Sunlight reaches Earth's atmosphere and is scattered in all directions by all the gases and particles in the air. Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.

https://spaceplace.nasa.gov/blue-sky/en/

Generally speaking, the first and main difference is that refraction happen upon transmission of the light, while scattering happen upon reflection of the light