Yes.
The sound from the instrument you plug into the INPUT A/MONO jack is output to the OUTPUT A/MONO jack, and the sound from the instrument you plug into the INPUT B jack is output to the OUTPUT B jack.
Yes.
The sound from the instrument you plug into the INPUT A/MONO jack is output to the OUTPUT A/MONO jack, and the sound from the instrument you plug into the INPUT B jack is output to the OUTPUT B jack.