1. Kinda tricky to answer, probably something happened to Nakabachi and he delayed it from his own will. The anime mentions something about "cold feet" but I'm not entirely sure if it's just an after-excuse of him, the exact time of the crash isn't strictly mentioned AFAIK. Past/present/future are all predetermined and "happen at the same time", the attractor field moves because of the D-Mail which already leads to SERN dystopia and Suzuha coming from some other worldline. It's the act of SERN acquiring the time machine technology first before anyone else (as in Beta), theoretically it's possible to be reached even without the D-Mail as long as they gain that knowledge first. The original worldline was most probably never active, and the coming of Suzuha happens from some other similar world line which makes things hard to wrap around, we don't really know what happens in the 0.000000% divergence and it's existence has been overwritten countless of times it might be entirely in the theoretical realm.
2. Mostly foreshadowing, mood setting, symbolism. There might be some deeper meaning to it though, and it has been referenced again in flashbacks and stuff, but I can't say anything more.
3. It's not important. The only reason Okabe undid all these D-Mails was because he lost the IBN in all of these worldlines, and logically moving back to the start point will make him acquire it again. Without it, he can't access the database and delete the first D-Mail which started it all.
4. Everyone's memories get overwritten when a world line changes (that is from inactive to active, no parallel world lines exist). Reading Steiner acts as a sort of a bug of that process. For the outsiders, he suddenly changes into a different person with different personality and no memories of the past.
5. If we assume the world line changes, he might witness it as simply vanishing like how the other world line changes processed so far. The scene is left vague so there are different theories about it and whether Steins Gate world line was reached immediately after or a bit later (the moment papers are burned?) is left to interpretation. There are also some conflicting views between different source materials and I'm not sure exactly which is considered the final ultimate canon.
Although, I like the theory which says he doesn't experience Reading Steiner at all because the past is effectively completely identical to that of the Beta world line and there is no conflict within his memories, even though the others don't remember it, and Suzuha and machine cease to exist immediately after they board it from the past... but then again he is left with a wound and others still on the roof which makes things really weird, could be some sort of attractor convergence effect similar to Mayuri's death that dictates Okabe should be wounded on that time and others should be on the roof for whatever reason even in the Steins Gate world line, or it is some weird effect similar to the D-Mails where they are send from another world line but still persist as an evidence in the new one. |