Yes, OT, TID and SID, Trainer Gender needs to match the new owner.
I've not tested if your ownership matters in Masuda Method. (In the sense that you own the ditto but changed the Language)
Presumably not.
Back in Gen 3 or 4 days, I think the issue is people were trying to create a flawless Ditto, and to avoid dealing with the PID/IV/Nature correlation in those gens, their standard move was to set the Ditto as bred.
Except Ditto cannot be bred. And since they don't know how to deal with the PID/IV/Nature correlation in those gens, they ended up not being able to make it.
So it's not that Ditto coding was different from any other mon. It was simply the encounter details were different.
In that sense, Ditto was similar to a Legendary mon in those gens (as in it can't be bred).
People too, needed to deal with the PID/IV correlations for Legendaries, in order to Gen a Legal one.
There's no correlations in Gen 8 games (beside from raids), so it's easy to make flawless Ditto now.
I assume you mean you don't see it in Misc tab on PKHeX.
The personalinfo file in every game determines base stats, evolutionary group, breed group, level up moves, tutor moves etc.
It's not a save thing. It's a rom thing.
In terms of save related, yes. There's a byte that gets set for Gmax capability, and the "recognition" of the byte doesn't exist in past gens. Thus, even if you try to hack the value in that location in a pk7 (for example), Bank -> HOME would ignore it.
Nah, they can be (illegally) brought down. PKHaX (hax mode) supports downgradings mon.
If we can recognize how "what byte represents what", and make it into a program,
then we can arrange that data in a way that it represents a mon from a lower generation.
The official methods just don't wanna support it.
No, they just Dynamax (instead of Gmax) when you opt it in battle.
I'm unsure how PPs work, but basically if you opt to Dmax/Gmax, the move changes based on the moves original type.
Besides the restriction of Dmax/Gmax, don't see how that is related to environment.
Also I edited your text's font color. For some weird reason, they were all white.
It's as tho you copied it from another post or something.
I'm not in dark mode (and I guess a few others aren't), so font background and font color really matters.
If the colors aren't default, then it may not be visible to others in different themes.