sceptios

I'm pretty sure Gen 3 is the only Gen where shinies exist but without a way to boost the shiny rate. Even Gen 2 has a shiny breeding method.

The Masuda Method was introduced in Gen 4, and then updated to have a higher shiny chance in Gen 5. You might be thinking of the base shiny rate being doubled in Gen 6. https://bulbapedia.bulbagarden.net/wiki/Masuda_method

Platinum sets the Fateful Encounter flag on the Darkrai and Shaymin in-game encounters. Set the origin game to Platinum and check the "Fateful Encounter" box under the Met tab for both Pokemon. They should pass Transporter's checks after that.

If you want it to default to a different game, you need to change the Blank Save Version in the settings.

If you're not too picky about perfect region emulation, you could always use use PKHeX to edit the Vivillon form of a new save. Then any of the Scatterbug line caught with a correct Luma locale set for the save should be legal (as far as I'm aware). That's how I got the 3 EUR region exclusive forms that I couldn't get with my USA and JPN systems legitimately. I realize this PKHeX functionality was brought up earlier, but it didn't look using it to edit the save was actually suggested.

I'm seeing odd behavior with Pikachus too. Mine is a Yellow starter with the correct catch rate of 163, but PkHeX (including the dev build) reports it as from Crystal. 025 - PIKACHU - A90F.pk1

I'm pretty sure Checkpoint/JKSV should work for any non-GBA VC game just fine, real or fake. GodMode9 is needed for GBA VC save extraction because the 3DS stores GBA saves differently.

Max Lair shiny odds are 1/300 (or 1/100 with Shiny Charm) and are always star shiny. If one is shiny, it will only appear shiny when you're selecting one to keep at the end and will always appear non-shiny during the battles.

Switch saves are always stored in internal Switch memory. Checkpoint is always on the SD card. Moving game data only moves the data of the game itself and nothing else

I also have a level 9 Pidgeotto caught in Viridian Forest (Yellow) that is marked as illegal for not having a third move. Pidgeotto doesn't learn a third move via level up until level 12. And a level 3 Pikachu from Viridian Forest (Blue) with 2 moves that PKHeX says should have 4 moves, but it doesn't get its third level up move until level 9 and fourth at level 16. (Or levels 6 and 8 in Yellow.) 017 - PIDGEOTTO - 2482.pk1 025 - PIKACHU - FD84.pk1

Saves for Switch games are not stored on the cartridge. They are stored in the Switch's internal memory. To answer the other part of your question, a SwSh game+dlc save will work with any combination of physical and digital game+dlc.

I just want to say thank you to @theSLAYER for taking the time to improve the IV display. While the previous display was good enough for what I needed, this new version is much better!

IV information is already displayed on the website for Pokemon with wonder cards. Check the displayed markings. For example, this one is 31/?/31/31/31/? and this one has 3 random 31 IVs

@theSLAYER Good to know. Thanks for the explanation.

@SkyLink24 I take it this means that if I evolve a Nincada that's been in Home, both the Ninjask and Shedinja are now safe to deposit. Right?