My first Gen III game was Emerald (which is the only one I had as a kid) when I was 8 and I was pretty dumb.. I didn't even know about the Regi's, I looked in Shoal Cave for a Spheal nothing more, and Sky Pillar - damnn. I didn't know about the Mach Bike thing so no I kept failing. I ended up giving up before the Elite 4 because I sucked so bad.
The next time I picked up Emerald (still only had Emerald) I had a Guide Book so for Shoal Cave I did it easily. Sky Pillar I had to try a million times but I got Rayquaza in the end. And the Regi's I tried Regice and I got it easily, Regirock was harder and I never managed to get Registeel.
Now if I try I can do all three with my eyes closed lol