Hello Daniel,
“The last one is a Mind-Door-Process only?”
Yes. The third type is a Mind-Door-Process. It is recalling a memory or namagotta.
“Could an arupa brahma memorise and visualize things or remember sounds of music once heard?”
Yes. All past memories are in the vinnana plane (or vinnana dhatu). Recalling memories requires only the hadaya vatthu. No pasada rupa needed.
– It is not really a “seeing event”, “hearing event”, etc.