I think you're wrong. He was stating two unlikely extremes.
OK well I'll give you some feedback then.
The others have covered this. Generally not so much but you can find, for example, Buddhist restaurants that have dishes containing fake meat.
Bodaiju in Mita, Tokyo used to be one of them but apparently they are no longer.
In terms of culture, of course there are ethnic foods in Japan. Chinese, Korean, Indian, etc.
If you're talking about indigenous culture then you'll see regional differences, mostly due to the differences in locality. (Examples below.)
You mean the same food has different flavors? Like Pokky? If so, it's mainly marketing. But it's marketing based on the fact that Japanese are very attuned to the seasons. For example every year they bring out the summer beers which I suspect are the same beers in different cans. Not sure.
A good example of a seasonal sweet could be sakura-mochi. I think it tastes mostly the same as other mochi though except for the leaf wrapping. Anyway I think there are more seasonal foods or seasonal variations than there are different flavors of the same food.
The dango example you mentioned I think is related to all the other seasonal variations such as Pokky. Tradition & marketing.
Yes for sure. I think others have covered this. Mainly due to differences in regional crops, seafood,etc.
A good example is ramen noodles. They vary across Japan, mainly in the broth. From the traditional salt or soy-sauce based to the tonkotsu (pork broth) from Kyushu or miso from Hokkaido. Okinawa has a very different food tradition than the main islands also. It tends to be a little more Chinese-like with many pork-based dishes. Of course if you are considering a something like a venn diagram, the overlap in what people eat is much greater than the differences.
I don't think so. Rich people eat more upscale food but it's more or less the same kind of food. For example you can easily spend $100 for a sushi meal. And you can go to a fast-food style kaiten-sushi place and get the same quantity for $15. In other words there may be differences in ingredients or quality or dining experience but I think not so much difference in the actual kinds of foods.