is the sun really on fire?

I will try to answer your question in a straightforward way without any snide comments. If you take 4 nuclei of hydrogen and exert enough heat and pressure, they have no option but to fuse together. This forms 1 nucleus of helium, but because the 1 helium nucleus is lighter than the 4 hydrogen nuclei, the remainder is given out as radiation. Nuclear fusion does not require oxygen in which to occur. This means the Sun loses mass at the rate of about 4 million tons per second, so should give you a picture of just how vast the Sun actually is, as that loss is what we see as heat and light.

The sun isn't on fire. Although the sun is plasma, and so is fire, there's some differences between the two.

The sun burns through nuclear fusion, not combustion. The "burning" is the energy given off when atoms fuse together.

the sun needs no oxygen to burn, it is a huge fusion reaction that can burn in a vacuum. its hottest part is its core. It feeds off of itself and requires no external stimuli to generate it's energy,

There are no flames on the Sun.

Are u kitting me? Are you asking how hot sun is? I thing that is a silly question because the sun is like a fire so are you crazy? Imagine! then you would know it because it hotter than fire you will burn

It is nuclear fusion, doesn't need oxygen.

no

google "nuclear fusion" and come back later