What is the RNG manipulation method in FRLG? And how do I do it?

Question

Now I know this question has been asked before in a different context, but I am asking for FRLG specifically AND I ask for an explanation of shiny frames also tell me a guide on how to do this method as the other question didnt really help with that

Comments

Couldn't you just make an alt account to do it? (assuming you are on a switch)

---

Yeah but I want this shiny on my main for all my other games for when it gets home accessibility. I only have online on my main account and would want to battle with it like in champions or something

---

https://pokemondb.net/pokebase/436458/can-i-trade-with-1-game-card-and-2-switches?show=436458#q436458
You can switch the account you're withdrawing from to your alt, and then switch back to put it into your main (it's my question, I know)

---

You can do that?!

---

I only learnt because of smart people on this site