Hair dye? HELP PLEASE?

The first time I dyed my hair, I got a blonde color and without bleaching it, my hair turned goldish brown which I liked. After 3 months or so, my roots started to show up so I dyed my hair into a brown shade. My hair turned dark brown. It's like a natural dark brown. Since it's been a year since I last dyed my hair, my roots were very visible and my sister kept complaining at how ugly it looked so I finally decided to dye my hair again. I got a medium brown hair dye but it turned black :( i don't know why it turned black and I hate it.

Today, I decided that I want to keep half of my hair black and half red. so all the hair underneath will be red and I'm keeping the top layer hair the way it is. I thought "oh well, black is close to my natural hair color anyways so i'll just keep it. but black is so boring but and i don't want to keep redying my hair because of my roots" So that's when I decided I'm gonna dye my bottom layers RED :D

Although I said "red" the dye I ordered is actually magenta.

I'm going to be using L'oreal HiColor Magenta with a 30 volume developer.. my questions are:

1. Will I need to bleach my hair since it's black?

2. Can I use the 30 volume developer to bleach is?

3. How do I use the developer to bleach my hair.

4. Will I even need to bleach it because the L'oreal HiColor Magenta I ordered online is for Dark Hair.

5. what will magenta hair dye fade to?