After learning a bit about RNG manip I don't get how shiny pokemon work in Fire Red

Hi guys, this is totally a noob question but I need to know. I've been trying to SR my starter to get a shiny for the past few days and got tired, so I tried to learn RNG manipulation. However, I didn't make it very far as these days my internet bandwidth is very limited and I rather wait until it's working properly again. The thing is, as far as I got, I learned that you can get a specific frame where the pokemon is going to be shiny 100%. So what I need to know is, does this frame change on every soft reset? Because if that's the case then I guess I shouldn't worry and just keep trying until I hit the proper frame in one of those SRs, but if it's supposed to always be the same frame between SR then that's a different story.

Thanks in advance!