Why didn't anyone develop an Android emulator on an Apple phone or an Apple emulator on an Android phone?

Apple's mobile phone is independent of Apple's system, and other mobile phones can't buy the right to use the system, while Android can make their own mobile phones based on Android as long as you give money. Now, all mobile phones except Apple are Android, and they are basically old and dead. Both sides want to eat each other. Apple's system is the biggest secret of Apple. If you make it, you will go to jail. It is even more impossible for Apple to make an Android simulator to help promote it in disguise. If you make an Android dream, you will wake up laughing.