Everything I'm about to say pertains to my own perspective and experiences on SubaHibi, so this should all be taken with a grain of salt. Also, it's really long and contains major spoilers so I'm concealing it.

Here are my answers to you on those points you bring up as "A" and "B" (and C for the question on Zakuro):

which is by default given to every "complete" existence when born. So in a sense, it's saying that people who are born but end up broken can still grab an opportunity to be reborn, for all we have is our internal world. And of course, SubaHibi also shows exactly what causes people to break themselves, in not accepting their existence, and consequently, their own birth into this world. If you look at someone who's mentally unstable and/or hospitalized, your "exterior" viewpoint (the initial impression) immediately sees a person who could never be happy. SubaHibi is trying to show the audience the inside of such a person and that they can indeed find their own happiness again. ")

on the 向日葵の坂道 end, that Yuki's existence is essentially the "soul". As seen in RH1, Yuki is the 世界そのものの少女 and a lot of the narrative throughout the chapter seems to be implying that the world is shaped by her will and desire, then that is reflected onto another world. I think when Yuki becomes aware that she is the World Girl, that transitory world starts to contract as she would be nearing the decision of whether or not to be born into the world ahead. She decides the former in this case, desiring for RH1 to have been but a passing dream. Thus as a result of her desires, it all becomes irrelevant to the rest of the story ahead. RH1 is basically a giant metaphor that portrays the same message. But in addition, it can also be the importance of thinking that; life is a blessing beyond what appears to be a curse, so you want to be born and live in it. ")

? What exactly does Zakuro's sequence of events remind you of? How about Kotomi's sequence of events (which I understand are only hinted at) from her as a child to becoming an adult? In the event 7 years ago, Kotomi can be considered the catalyst of, but in the reenactment of those events during July of 2012, Zakuro has taken her place as the catalyst instead. So I leave you with a few questions. Is Zakuro perhaps just a specter of Tomosane's unstable mind (representing Kotomi, yet a part of himself as well) that he placed in his internal world to direct it, leading to the story's particular outcome? She did appear in his "pre-birth dream", after all. Is her entire perspective throughout Insects still his own perspective, yet he believes a person pertaining to his circumstances to exist and influence the world around him? ")

I really hope that I was able to present this in the least convoluted way possible, but I understand my words here are already pretty much in category of being entirely "far-fetched/crazy". I guess think of this post as just a way to get thoughts flowing on the problems SubaHibi's mysteries raise. It's most definitely not as complicated as I make it sound with this sea of words, so I recommend to keep discussing it with other people and take a second or perhaps third look at everything. (Especially )

Now, as for the reason why I sound so confident and convinced in what appears to be just another subjective interpretation on the story (which it technically is, I understand). I think that SubaHibi's story, as an 'unsolved equation', most certainly has its entire answer embedded somewhere within the story. It's just in such a place that no one would ever think to look.

SubaHibi. Still don't recommend actually picking it up though. It's merely the previous version of RH2, Invention, and Insects, and then it ends. ")

Wow, that was terribly long and could've been trimmed. Anyways, I hope this, in some way, helps you on gaining more knowledge about SubaHibi. Otherwise, if you want to take the more 'fun' route, which is making connections in the story via the references and philosophy, then that's also an option for understanding the messages/themes/concept. It didn't really help me too much in understanding those (btw I only read Alice, Cyrano, Night on the Galactic Railroad, and a tiny portion of the Tractatus, so...), but it was fun for the time that I had in reading that stuff.