Question : Problem: How to make a 4 wire phone crossover cable

Using a cat5 cable, terminating with rj11, what is the pin-out for each end of the rj11?

Answer : Problem: How to make a 4 wire phone crossover cable

That's a tough one. There are dozens of serial/RS-232 configurations however, a typical phone extension crossover is as simple as:
RJ-11 #1        RJ-11 #2
   pin 1    =>     pin 4
   pin 2    =>     pin 3
   pin 3    =>     pin 2
   pin 4    =>     pin 1

However, please do not accept this as correct for your purposes. You should verify with your supplier first, as the internal wiring of the serial adapter can be all sorts of configurations.