Black holes are a special case in that they have high-mass density, but galaxies, such as ellipticals, do not, and are comprised mostly of empty space, while both contain enormous mass. Black holes also do not radiate light or reflect it, they completely absorb it. This means the light from the occluded object will "radiate" outward, whether we see it from Earth or not--and whether it was originally completely invisible or not. But it also means that the light we're not seeing from Earth will be visible in sightlines elsewhere.
I also saw where you amended your question to include questions about whether lensing eases the field of objects available for study. The answer to that is an unequivocal yes. Hubble has been using the phenomenon to study occluded objects for years.
You can read about the ESA/Hubble here: https://esahubble.org/science/gravitational_lensing/
You may want to read up on Transformational Optics. This field deals with how light waves are bent and bend other nearby objects.