How is the sun classified? as a giant star as a medium star as a white dwarf as a neutron star

Sun is classified as G-type main sequence star and appears to be white dwarf from the space.

Explanation:

Sun is a white dwarf it consists of 99.86% of the mass of solar system and appears to be yellow dwarf through the earth's atmosphere.  The reaction of nuclear fusion, i.e. converting hydrogen to helium occurs in the sun as a process of fueling. Other white dwarf stars are namely Sirius, S R Scorpii, etc.

as a medium star

Explanation:

The Sun is a G-type star of the main sequence and luminosity class V that is in the center of the solar system and constitutes the largest source of electromagnetic radiation of this planetary system. It is an almost perfect sphere of plasma, with an internal convective motion that generates a magnetic field through a dynamo process. About three-quarters of the Sun's mass consists of hydrogen; the rest is mainly helium, with much smaller amounts of elements, including oxygen, carbon, neon, and iron. A star of this type has about 0.8 to 1.2 solar masses and a surface temperature between 5,300 and 6,000 K. Like other stars in the main sequence, a G-type star in the main sequence is in the process of converting the hydrogen element into helium in its nucleus through nuclear fusion.