GTX 650 isn't supported. FireFly needs the CUDA Compute version of 5.2 or higher. Nvidia made the compute versions extra confusing. Sometimes a higher number card has a lower compute version.

Here's the source from Nvidia: https://developer.nvidia.com/cuda-gpus expand the heading "CUDA-Enabled GeForce and TITAN Products" and look for your GPU in the list.

You'll find weirdness like the GeForce 910M is a 5.2 compute and so it's supported. But, the 920M, 930M and 940M are compute 5.0 and won't work for SuperFly.

I run different versions of Poser all the time. It will work as long as they are whole versions apart. So yes, you can run P12 and P13 at the same time. I wouldn't try rendering in both at the same time though.

Being that a big part of my job is trying to break Poser I have 17 different installed versions of 3 major releases. Different versions of the same major release can be installed together they just can't be running at the same time.