Most of this is possible. BUT, you will have to learn the routing.
To mono the input, go to SETUP/DSP A (or B as appropriate) and point the IN1,2 etc to your source (probably "analog in 1"). This will feed analog in 1 to all the preset inputs.
Monoing the output is a bit harder. To combine 2 outputs go to SETUP/OUTPUTS and set (say) ANA1 to both "DSP A out 1" and "DSP A out 2". This will sum 2 of the preset outputs and feed them to analog out 1.
If you want to mix 4 outputs as you suggest, you will have to load a mixer preset into DSPB and feed it from DSP A.
Basically, you have to read the manual. It's character building. Sorry.