The temperature at which various elements change phase depends on both the temperature they are at as well as the pressure they are placed under. If the pressure and temperature of any element is varied and the state it is at noted, we arrive at a phase diagram which is a graph divided into three areas in each of which the element has a particular phase.
0 K or −273.15 degree Celsius is the lowest temperature that can be attained. All elements turn to solids at this temperature even if they are placed at atmospheric pressure except liquid Helium. The special properties of Helium which is the least reactive element and also the lightest noble gas allow it to remain in the liquid phase even at 0 K. Only under high pressures does Helium turn into a solid.
Most substances found in nature exhibit a behavior where they change from solid to liquid and from liquid to gas as the temperature is raised. On decreasing the temperature the change in state is reversed.
In addition to temperature, pressure also plays a large role in what state a substance exists at. At atmospheric pressure it is possible to cool down all elements so that they are at solid state. For the element helium, in addition to an extremely low temperature (below 1.5 K) it is also required to increase pressure to above 2.5 MPa so that it changes state to solid.
It is not possible to convert all elements to the solid state merely by lowering temperature; for some elements it is important to apply an appropriately high pressure.
yes, at one point all elements can exist in solid form.
Yes, at one point all elements can exist in solid form. Although at different temperatures. But I'm sure if you lower the temperature low enough most elements can become solid.