Could it be possible to recieve the mix of FOH on QC, and listen to it thru the headphone out?
Yes.
Example: Connect the plugs of the FOH mix to the returns 1/2, create a empty row, patch the input of this row to returns 1/2 and the output to out 3/4. With the internal headphone mixer you can mix all outputs as desired, e.g. mix your guitar sound to the FOH mix.
However, I only have the manual, it is not described in detail, but that’s how it could work.
Thanks. for the info.