You're a bit confused on SR/HR. Hard resets are functionally the same as soft resets, they just take longer. What people meant is that you need to create a new save file every 50-60 resets.
Basically, this is how it works:
Shininess is determined by two things: a hidden personality value (PID) that every Pokemon has, and your save file's trainer ID (TID); when they "match" in a specific way, the Pokemon is shiny. In most games, you can count on the PID of every Pokemon you encounter being different, which means that each one has a chance of rolling a shiny PID. But Emerald's RNG is bugged with a fixed seed. This means that, if you encounter a Pokemon on, say, frame 5 after starting the game, reset, and then encounter another Pokemon on frame 5, they'll have the exact same PID. When soft resetting, you're often encountering your starter within a 1 second window, which in Emerald, means that you're effectively locked to 60 PID values, and it's entirely likely none of them are shiny. Because the starter is so early in the game, it's better to completely restart your game every 50-60 resets to scramble your TID until it matches one of the fixed PID values and allows it to be shiny. This is called an early shiny frame.
I should note that when I refer to the TID, only half of that value is the one displayed on your summary screen; the other half is completely hidden, which unfortunately means that there's no way to see if your TID will yield an early shiny frame except by trial and error.
