Just curious, in Gold/Silver/Crystal, is there a code to modify the starting Pokemon to any Pokemon like you did before and in Crystal is there a way to modify the clock like in Gold/Silver and change what baby Pokemon hatches from the egg? Any answers that aren't trolling would be appreciated!

I don't think so but if you google an encounter any pokemon code it will yield the same result. Just add a ton of Master Balls to your inventory and you will get it guranteed first try. It edits the pokemon you encounter to be the same every single time.