Let's just get that out there. Primes are all odd beside 2, so they must be an even amount apart. (Could also be other pairs like 5 and 7, or 71 and 73, but r must be 2.)
I can prove r is not 2 or 3 using modulo and difference of squares/cubes. Those have solutions, but they don't satisfy p>q>r because q has to be 2. I'm not sure of a method for exploring r = 5, 7, 11, etc.