Could you tell which pictures, which depict how the vowel chart is positioned inside our mouth, are accurate?

You cannot really project the whole vowel trapeziod into a single picture of the mouth because the shape of the mouth and the tongue actually change as you move through the chart. So any single picture such as the three above will be inaccurate.

The chart really depicts relative positions of the highest position of the tongue with the edges being the extremes thought possible. So any projection will be just a rough schematic suggestion. But 1 is obviously the closest to some semblance of reality.