Gen IV: Heartgold and Soulsilver freeze on emulator
I still remember the precious time with Pearl, Diamond, Platine and the remakes of gen II
But to repeat the title once more time: you can never play Heartgold and Soulsilver on No$gba nor any emulator because is gonna crash and freeze before you can reach to the 1st gym. And NO, NO action replay code will help you, so needn’t find them.
Instead, why don’t search for PerfectHeart and PerfectSoul at pokemonproject (I’m sorry I don’t really remember the website name but Google will help you the most) and try the desmume emulator (I think any version will do but the later the better)
Search for it, the person created PerfectHeart and PerfectSoul will give you the best instruction to install the games and also the advance of playing gen II’s remakes without got some freeze or crash