Setting aside how this might evolve or come to be, could a cell use liquid carbon tetrafluoride(CF4 becomes liquid below -130 Celcius) as a solvent instead of water? Assume that the cells work perfectly fine at this temperature.
That's a very solid "maybe".
Non-polar? Well, the chemistry won't be the same as we have in water, but that wasn't gonna happen anyway. Plenty of sci-fi writers and actual scientists have seriously proposed the possibility of life in non-polar solvents like ethane or liquid CO2, so why not CF4?
Small liquid range? Not a problem if the environment has a stable temperature.
Highly stable? OK, so it's just a solvent, not a participant in reactions. Water is weird, there's no reason we should assume that a biosolvent must itself be chemically active.
Really, what we want is for it to be able to dissolve a lot of other stuff that can react, not dissolve absolutely everything, and for it to support spontaneous liquid phase separations.
Fluorocarbons are both lipophobic and hydrophobic, and CF4 is partially miscible with CH4, producing separated phases at high concentrations. So, you can probably get some kind of micelle, and combinations of oxycarbons, charged nitriles, fluorocarbons, and hydrocarbons could plausibly form surfactants to produce bilayer membranes.
It'll dissolve gasses really well, and nitrogen, hydrogen, and oxygen are all still gaseous at those temperatures. It should dissolve a variety of complex fluorocarbons fairly well. And while they are not common, there is a small number of natural biogenic fluorocarbon compounds produced by Earth life, so biochemistry manipulating carbon-fluorine bonds to produce and use those complex fluorocarbons is clearly plausible.
But, what else can it dissolve, and what reactions can actually take place at those temperatures? Who knows?
Hal Clement (among others) thought life in liquid methane was possible, though, and there's serious astrobiological research into the possibility of life in liquid ethane on, e.g., Titan, and if we consider those to be plausible, using CF4 as a solvent doesn't seem that much more far-fetched, if we put aside the issues of how such a thing could evolve and just assume it was artificially designed or something.
I think carbon tetrafluoride lacks some of the useful properties of water to be a good substitute:
- it's non polar, thus it will have problems dissolving ionic substances and acting as a buffer for acid/base reactions
- being non polar its liquid state range is narrower than water
- it's very stable, making it difficult for any biochemistry based on it to have access to its radicals