The opening is not accurate, as evidenced by the Cheren episode. Besides, we don't know what the span of the Castelia Sewers episode will be, especially as it follows the Kanto Fair episode.No, not it cannot. That episode is at daytime and will deal with the sewers and Colress.
Again, the Liepard scene could easily be fit into any episode involving Team Plasma and Castelia City.The Genesect show up on the opening in tandem with the scene that was lifted from the two-parter. If it's dealt with, then the two-parter will likely be dealt with at the same time.
N is definitely not the king of Team Plasma at present, since he opposes them; there is most likely another reason for the confrontation. Do you really think that N will be missing from the last two March episodes?By your logic, N's past could be in the March 14th episode rather than get an entire episode dealing with it. And no, it does not need to be before the April three-parter, it could very well be in the April 4th episode when N fights Ash. I would certainly think revealing himself to be the King of Team Plasma is a good reason for Ash to fight him over.