different voicing to bring out the individual characteristic of each instrument.
only electro acoustic and be plugged into electric guitar amp and vice versa. Whether sound good or not, its another different thing.
everything, start with low volume and onwards
bass into guitar amp also can, guitar into bass amp, also can, as long input to output to input. At least thats what i have been doing and my amp still surviving. Important things is low volume for bass into guitar amp with bass knob almost at 0...