Hair Dye Questions

Hey. I’m dying my hair for the first time. I can’t use permanent dye so I’m probly goint to use Clairol’s Natural Instincts and dye it a really dark brown. I’ve heard a bunch of horror stories about black semi permanent dyes going wrong so I’m kind of scared lol

First question: If you use/used Natural Instincts was it good or bad and if it was bad what’s a better dye I can buy at a drug store that’s semi-permanent and will last a long time? (I’ll be doing it at home so you know)

Second Question: I know it’s silly but I honestly don’t know. If I dye my hair dark brown all over, would it be bad for my hair, stain it or become discolored if I used a blonde dye on top of it to do coontails? (I don’t know much about hair color and I wanna make sure I don’t burn or damage my hair)

Third Question: I’ve seen Fanci Full and I don’t really get what it is… How do you use it and what’s it do?