We'd need a better RNG Reporter for Gen 3. Via ID abuse (which is poorly documented for Gen 3), it is possible to get 6IV Shiny Timid spreads for Emerald of all things.
Barring that, more poorly documented things would include that R/S have 100% exploitable RNGs like Gen 4/5 in that they don't always start on the same seed provided the game has a working real-time clock/internal battery. Something like that would probably allow some previously unheard of IV spreads.
The current RNG reporter is fine for 3rd gen RNGing. ID abuse for dead battery R/S is well documented (no point in doing it with a live battery unless you
really want a novelty TID/SID combo), ID abuse for FR/LG/E is poorly documented but is also strictly emulator only territory, which is often poorly documented anyways.
Live Battery R/S is poorly documented because only a handful of people have done it due to the time, effort, and RNG knowledge involved, and the fact it uses a (somewhat) controllable starting seed only means that more spreads become feasible for retail abuse. The RNG is a loop, the seed only determines where you start and therefore how far away your target is, not what appears on the loop.
False. It lacks the Fateful Encounter flag and it uses the hatcher's ID/SID/OT.
PCNY Wish events were given out as Fateful encounters, but there was a (somewhat obscure) method of getting them without the Fateful flag when hatched. I've not transferred any legal ones to X/Y to confirm the Fateful flag remains, but I see no reason why it wouldn't.
In no generation of Pokemon games does the baby retain info about its parents (Egg Moves or Poke Ball passing doesn't count. You still can't tell much about the parents to know if they had an illegal PID/etc.) - which is the only way you would know a glitched/hacked Wish Chansey/etc from an event one. It's sad, but true.
FR/LG eggs use one method of generating the IVs/PID (technically two for different parts that combine to form the finished egg, but you get the point), the PCNY Wish events used a different and comparably very limited method of generating the IVs/PID. You're better off buying a lotto ticket than hoping your randomly bred egg will have recieved an IV/PID combo that happens to be legal for both methods.
There's nothing that would identify it as "definitely/possibly event" or "legally hacked/glitched", both are the same.
There is of course no way to identify a true "legally hacked/glitched" Wish Chansey, but you're not likely to get one just by throwing a Chansey and Ditto into the Daycare and hacking/glitching Wish onto it.