TCRF has the exact implementation documented. One thing that’s commonly missed in the urban legends that get passed around about the game is that the two hardware checks prevent the game from running at all. It’s only the ROM checksums to see if those routines were tampered with that will then trigger hard mode. The point of that is to trick anyone trying to crack the ROM who might think they succeeded if they got their modified ROM to boot on a cartridge copier.

But this does mean that unless you modify the ROM, no emulator will ever trigger hard mode, an unmodified ROM will either run or it won’t.