Why do not the coniferous trees fell their needles in the autumn?

Because a needle is completely different than a leaf. It has thick walls, is better to keep the fluid level in the cells etc. If they loose fluid level/-pressure, the do not collapse because they are stiff and can therefor handle a dry season better than a hardwood.

Coniferous trees drop an entire group of needles, with the same age, at a certain time during the year. Scandinavian Spruce for example, let their cohort in late winter. I remember that especially well as my first ski race took place in late March in northern Sweden. My dad had waxed my skis with silver paste wax. It looked very nice under the skis before I started "skiing" around among the needles. The skis did not slide an inch, but I had to walk around the one mile long track. It took years before I appreciated skiing again.

But how do the needled prevent themselves from not freezing and burst? Because they reduce the water volume to a certain point and increases the concentration of both sugar and minerals to get a glycolic effect, and thus lower the freezing point of water