Can I soft reset during Swap Breeding to get a different ability and/or IVs?

Question

I'm trying the Swap Breeding Method for shines in my Pokemon Sun, and I'd like to get a shiny Modest Anticipation Eevee w/ 5/6IVs to trade into my Ultra Moon file.

On my first round of this, I hatched my shiny Magikarp on my 16th egg, soft reset the game, swapped Magikarp for a regular male modest Eevee w/ everstone, collected 15 eggs into my PC and only hatched the 16th Eevee egg(shiny). It worked, however; the Eevee's IVs were trash.
I didn't wonder this until my second round but,

Could have I saved the game BEFORE the nursery helper had crossed her arms to indicate she had the 16th egg (again, this was the shiny one), hatched the Eevee, soft reset, hatched it again, and done this over and over again until it had my preferred Ability and IVs? Or are they already rolled when I had hatched the magikarp and cannot be changed? If this can work, will the Eevee still be shiny?

Comments

You can test this yourself, can't you?

Answer 1

The IVs themselves weren't rolled when you hatched the Magikarp, but the inheritance was. For example, if your Ditto held a destiny knot and had perfect IVs, and your parent Eevee had a spread of 1/2/3/4/5/6, and the child's spread was 1/15/3/4/5/6, then that means the child inherited five IVs from Eevee and the physical attack was randomly generated. In order for the re-rolling to work, you need to replace the parent Eevee with a different Eevee whose spread was 31/doesn't matter/31/31/31/31. The resulting physical attack IV will still be 15 because that was randomly generated, but the rest of the IVs will still be inherited from the Eevee, and therefore will be perfect.
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