It is practically impossible. You have to have roots to bleach your hair and root on hair of at least a inch or more to safely bleach them. You don't want bleach directly on your scalp.
They don't.
long hair
Take half inch parts. Apply the bleach one inch from you scalp. Till the end are close to your desired shade. Than apply bleach to scalp. The reason for this is bleach works fast next to you body hot, and it will not come out even. We call it hot roots. You should really go to a professional, for this service. Bleach can kill your hair if left on to long.
no, it won't bleach your hair but it will dry it out!
3hours
Usually, any time after. But you should check the dye and bleach boxes just incase. If you can bleach your hair after, just make sure your hair can handle all of the chemicals.
When you bleach your hair, you are stripping all color pigment from your hair. You will need to wait for new hair to grow back for your hair to return to normal.
It will not hurt as long as it is on the hair. You should not touch the scalp or your hands with it as it will burn and you should never use household bleach because your hair will dissolve in it.
I'm not entirely sure what you mean by burning yourself. If you mean the burning sensation you feel on your scalp when you've applied bleach to your roots, then that means you applied the bleach to your roots too soon or you left it on to long. Every at home bleach kit comes with instructions for a specific reason; bleaching hair is severely damaging and can be (if not done properly) somewhat hazardous for your health. How lightening or bleaching works is it opens the pores of your hair shaft and breaks down and decomposes the melanin(color) of the hair. During the process it diminishes strength and the chemical bonds in your hair, which is why when some people bleach their hair it falls out. Bleach should have minimal to no contact with skin because it can be absorbed by your skin just like it can be absorbed by your hair and unlike your hair, your skin will become irritated and more than likely bleed. If you did happen to damage your scalp while bleaching, my suggestion to you is to gently rinse your scalp with room temperature water and don't rub or scratch, that will make it worse and could cause infection. Blot your head dry and avoid using heat. If you were bleaching your hair to radically change your hair color and your scalp was damaged, I strongly suggest waiting 24 to 48 hours before you complete your hair project, for the sake of your skin's health. The next time you decide to bleach your hair, please read the included instructions thoroughly and follow them precisely. I also think consulting a professional to learn more about your hair's texture, courseness and porosity to help you determine how long you should leave the bleach in your hair and when you should add bleach to your roots.
Hair bleach does not stay active for very long once it has been mixed. It begins to lose strength quickly and should be used within an hour.
You can leave bleach on the hair for up to an hour. After this it will not work. You have to make a fresh batch. The more time that the bleach is out in the air the less time you have to put it on the hair. The ends are dark because there is more of a build up of colour there. You will have to do this on a few separate occasions. Because your hair is black the bleach will take longer to take the colour out. Black changes to red, the orange then blonde, it does take longer to get black out.
24-48 hours
Around 25 Years.