Are emulators allowed or no, and of so what are the rules regarding, thank you.
I personally would not allow emulator runs on the leaderboard, but there's no official stance on this yet since it hasn't come up before. However if you're planning on running I-Ninja on emulator, I'd recommend looking into getting/downloading the PC version of the game. It also happens to be the fastest version to run due to several exclusive cutscene skips.
I haven't been able to find a good legitimate dowload for the PC version. If you could link one I'd appreciate it my man.
I bought my PC copy off either ebay or Amazon, can't remember.
I don't believe the PC version was ever released in the United States, so you'll probably have a lot better luck looking on European ebay or Amazon.
EDIT: I found some copies on UK ebay for about 5 pounds https://www.amazon.co.uk/gp/offer-listing/B0001PBCMO/