The horcrux technology uses the ghost phenomenon. Specifically, by causing the violent death of a wizard under controlled conditions (i.e., murder)

Some of the horcruxes in canon are made from murdering Muggles, though.

In chapter 45, the Dementor recognized Harry as Voldemort and addressed him by name: "Riddle".

I don't see anywhere that this happens in Chapter 45.

Alternative explanation: Magic oxygenation shots don't work because the inventors did not understand biology, just like the inventors of broomsticks did not understand physics.

Have you ever tried using a humidifier (at night or just in general)? Dry sinuses are way more susceptible to allergens, and there are plenty of ubiquitous allergens that could be responsible for your headaches no matter where you live.

It will not return any specific person even if you speak Google: a person -"Genghis Khan"

Yes. Also, "she saw the face beneath, and recognition sent a jolt of terrified adrenaline bursting through her" - 'recognition' doesn't read to me like the person she saw was a personal acquaintance of hers.

Grindelwald?

He's been mentioned so many times, and his connection to Dumbledore explored in such detail, that it'd be surprising if he didn't play a role in the story. If you grant that, then his motivation for returning was aggressively foreshadowed by Chapter 42 ("Courage"). He'd be a strong candidate for opposing and manipulating Dumbledore as Hat & Cloak is doing.

But not much in Hat & Cloak's appearances points to Grindelwald specifically. The sibilance of his speech and the ambiguity around his gender might be nods toward stereotypically gay characteristics. And might not be. It'll be clearer once Eliezer's told us more of what Grindelwald was like as a person.

The more I think about 55-56, the more potential holes I find.

McGonagall (or people from the Ministry) successfully detected the use of a Time-Turner before, in Ch. 18. So they will detect it now and all clues will point to Harry. It can be patched over by saying Mary's Room (or Quirrell's wards) makes the event undetectable.

I don't understand the rules regarding Patronuses. Can't McGonagall ask her Patronus where it found Harry, if Dumbledore can ask his Patronus similar questions? Or, alternatively, can Dumbledore send his Patronus to Harry, like McGonagall did, and then ask something like "is he here in Azkaban?"

To everyone saying Harry will create a third copy of himself to save the day: he can't easily do it without Quirrell's assistance, because the Time-Turner is locked. One possibility would be for him to find the original Quirrell and ask for help.

Anyone who wants to can wear perfume/cologne (it's essentially the same stuff, just a different word for a different gender of user). If you're wondering whether you should try it, then try it! Go to a large department store and try out their testers, then walk around for the day and see if you and your companions like it. The effect immediately after application is often not the effect after it airs a bit. You can even try mixing scents. The one thing I strongly recommend is to avoid the really cheap stuff. If the budget is tight, try different good high-quality scents for free for a while, so you can be sure you'll like what you get.

The way I've seen perfume applied usually sprayed on one wrist, then the wrists are rubbed together, and then the wrists are lightly touched to the neck and clothes. This avoids getting too strong a smell, and if you overspray the wrist, you can wash it off.

When I use cologne, I spray it in my armpits instead of deodorant, and maybe on my throat. That's not necessarily typical--it's sort of the old way cologne was used, and works for me because I have light BO. You can also use cologne the same way I described for perfume.

In the U.S., cologne is not usually considered an appropriate substitute for deodorant, but individual tastes run a broad gamut on that. Some people are allergic to most perfumes and colognes--they do have actual botanicals in them.

Wow. That is a very thorough answer. Thanks!

exact procedure for boiling

Dump vegetables into a pot. Pour in water or stock until it reaches the same level as the veggies (less if you plan to add cream, more if you're nervous about burning it, less if you want thick goopy soup and more if you want thin soup). Put it on a stove burner, turn it up to High, stir at least once to prevent stuff from sticking to the bottom, and check on the smooshability of the vegetables every 5-10 minutes. Add more water if the vegetables are still unsmooshable and the water level has gotten significantly lower.

what sort of spoon

The only reason this would matter would be if you use a short-handled spoon, you will have to have your hand much closer to the boiling water, which is physically uncomfortable. Otherwise the spoon could be wooden, plastic, metal, slotted or not, whatever.

I think there may be some psychological element to finding one's own recorded voice unpleasant. When I hear my own recorded voice played back at me, I find it incredibly unpleasant, but my acquaintances assure me that it doesn't sound bad to them. Likewise, I've had people tell me that they can't stand the sound of their own recorded voices, when they sound perfectly fine to me.

If your acquaintances agree that your speech could use work, I agree with the recommendation of speech therapy, but it's possible that the problem is in your perception.