Q: iPhone 7 Plus camera issue

Any camera pointed towards a very bright light source will be prone to lens flare.  It is particularly common on very small lens digital cameras.  Its not a bug or an error - it is a simply phenomenon of physics and the limitations of a lens with intense direct light input (http://www.cambridgeincolour.com/tutorials/lens-flare.htm).

One way, sometimes, to get rid of it is use one cupped had around the lens as a temporary cover or hood to reduce the side incident light hitting the lens (this is in fact why large DSLR lenses and spotting telescopes come with a hood, to reduce lens flare).

I too have been taking pictures my whole life, or well at least the last 40+ odd years if it. What you show in your shots looks indeed like classic lens flare. If I point any camera I have ever owned, from point and shoot film and digital to SLR and DSLR setups, at any bright light at the right angle to that light, I can reproduce that sort of effect, no problem.  Some goes for any previous iphone I've owned when shooting into sunlight or other strong light sources.  The price of the device has nothing whatsoever to do with the physics of light and lenses.

If you feel it is a defect if some kind, then you need to make an appointment with Apple and ask them about it.  You posted screen shots and asked for people's interpretation of what you showed. I stand by my take on what you show in those pictures.  If you wish an actual evaluation of your device by Apple, then you need to take it into Apple.