>>42775847From what I hear and what seems to be the accepted standard is every pokemon has a x% of being shiny. For example lets say Shuckle's shiny chance is 1 in 420 or .0024 :>
This is known simply as RNG (Random Number Generator)
Now, does that mean if you check 420 Shuckle that you'll be guaranteed one? No, that's just it's percentage, you can check thousands and not get one. On that same coin, you can check 20 and get 2 shinies, you just never know.
NOW for the order, no. Changing the order of what you check/catch will not change anything or people would have figured that out years ago. It's VERY easy to figure out if every 420 checks of a shiny eligible Pokemon will be shiny. That Rattata had the same odds of a shiny as that Pikachu, it just happened Pikachu was and Rattata wasn't.
tl;dr RNGesus is your lord and savior, make your offerings and sacrifices carefully
Now then, back to trying to hatch a shiny Happiny. Only 20 in and 3 regulars but I did get a 4* Magikarp from an accidental 2k. WIsh me luck anons...