Sorry for joining in late and going back to the initial post, but I'd like to share my opinion on some of the plotholes/unanswered questions mentioned at the beginning of this thread.
TheOtherOne wrote:
* How was Eurus actually "written out" from Sherlock's memories? (That's what she claimed in TFP).
I'm not a psychologist, but the human brain tends to suppress negative experiences or to rewrite memories. Especially children are quite open to suggestion. If someone keeps telling a child long enough that something happened in a certain way, he/she will start believing it and even mistake it for his/her own memory. I guess something like that happened to Sherlock after Victor and Eurus had disappeared. The memories were so painful that he fully suppressed any memory of Eurus (who had caused him that pain) and rewrote the memory of redbeard being a dog instead of a person and that he was put down for some reason. And I guess Mycroft and his parents - understandably - did nothing to remind Sherlock of what really happened but encouraged the false memories that were much less painful than the real ones.
TheOtherOne wrote:
* What were Sherlock's trigger words that Mycroft referred to? (Aside from the obvious one... Redbeard).
Redbeard and the whole East Wind (= Eurus) story from HLV.
TheOtherOne wrote:
* If Moriarty's little "miss me" video was really Eurus all along, what did Sherlock "think" it meant when he told everyone at end of TAB that he knows "what he's going to do next"?
Probably he just meant it in a general way: He knew exactly that Moriarty would next do something to him, Sherlock, and he would just have to wait and see what exactly that would be. Or he was just bluffing there, making himself seem indispensable so they would give him a pardon.
TheOtherOne wrote:
* If Moriarty knew Sherlock would end up in the locked room with Mycroft (Holmes killing Holmes) as part of Eurus' game, that meant he knew Sherlock would survive the fall! Why hire those assassins to target John, Lestrade and Mrs. Hudson??? He set all that up just to kill himself?
I don't think Moriarty knew/thought Sherlock would survive the fall, but there was always a possibility that Sherlock could decide not to jump and let his friends be killed instead. In case that should happen, Eurus had most likely promised him that she would finish off Sherlock in Moriarty's place, using those videos he had to send her to torture him. By "Holmes killing Holmes" Moriarty could have had Eurus killing Sherlock in mind, not Sherlock killing Mycroft. I don't think Eurus told Moriarty any details about the game she intended to play with her little brother. There's only so much you can talk about in five minutes . . .
TheOtherOne wrote:
* Who is posting those "Miss Me" and "Miss You" DVDs for Mary post her death?
She could have told anyone of her friends or work collegues to post those letters in case of her death/a few weeks or months after her death. They would just have had to check the obituaries every day in the paper.