A problem in NP can have a (positive) solution verified in polynomial time. That's it. Requiring more than polynomial time to solve isn't part of the definition, and in fact it's an open question whether any problems in NP require more than polynomial time to solve.
Every single problem in P is in NP. What is believed but unproven is that some problems in NP are not in P.
Hard mode forces most people to play smarter than they usually would. I'm not sure if that's the same as being easier. Hard mode is certainly harder for a skilled player, because that player could play normal mode as if it were hard mode but without having to worry about avoiding hard mode traps like _IGHT or SHA_E--if they encounter such a scenario they can just play known-bad words that check several possible solutions at once (e.g. FIRES for _IGHT to check FIGHT/RIGHT/EIGHT/SIGHT).
The inclusion of a timestamp in v7 makes collisions impossible unless the generating systems think that the time is the same down to the millisecond, which makes the temporal distance quite relevant.
A "review of media reports" is not going to capture any incidents that the media didn't report on. That doesn't strike me as likely to capture every incident, or even a majority of incidents.
"Ghoti" is an artificial example that doesn't actually work if you account for the way positioning affects pronunciation. Pull up a list of words that start with "gh": none of them (unless "ghoti" itself is on the list) start with an /f/ sound. You'll find the same for words ending in "ti" and the /ʃ/ sound.
I recommend asking people how "ough" is pronounced instead. Cough, bough, though, thought, through, thorough, hiccough--enough!
> What are you talking about re: space shuttle and tens of millions?
GP was almost certainly referring to "They Write the Right Stuff," an old article that is pretty well known in spaces like this. It discusses a process that (a) works extremely well (the engine control software was ~420 kLoC with a total of 17 bugs found in a window of 11 versions) and (b) is extremely expensive (the on-board shuttle software group had a budget of ~35 million per year in mid-90s dollars).
The Natrol liquid isn't usually too hard to track down. They advertise it as 1 mg or 2.5 mg, but it's the same stuff, the bottle just direct you to take 4 or 10 mL respectively.
It's not actually optimal. Each check should account for all previous feedback, but it may be optimal to make a known-incorrect guess and trade the chance of winning with that guess for additional information.
For example, if your first guess on wordle is BOUND and you learn that the word is _OUND, you know the answer is one of FOUND, HOUND, MOUND, POUND, ROUND, SOUND, WOUND. Satisfying all previous feedback leaves you checking those one at a time and losing with probability 2/7. Or you could give up the 1-in-7 chance of winning in 2 and trade it for certainly winning in either 3 or 4: HARMS checks four of those options, and WHOOP identifies the remaining three.