Custom firmware for PSP-2000 with the TA088v3 and above motherboard and PSP-3000 by the PSPGEN team. Please note that this custom firmware does not work with PSP-1000 and PSP-2000 with the motherboard that is below TA088v3.
I don't have a wii u anymore to test it myself, but if homebrews are not visible on the wii u menu I think you can press L + R + minus to open the plugin menu, there should be an option called "homebrews on wii u menu" or something similar
Or when your player dies, you can say in code, if enemy exists, do nothing, but if enemy does not exist, then create enemy at certain spot. (This would be a pain tho for lots of emeies)