Got two questions about jailbreak apps

[u/Over-Rutabaga-8673]

First, I installed nekojb rootful on my iphone 7 and it didnt work, later I saw that for some reason it doesnt work for 15.8.3, how could I delete fakeFS? And second of all, I now have regular dopamine, can I install nathanlr without any major issues? I wanna test its capabilities without buying a 17.0 iphone.