You can use it as long as it hasn't been opened9the bottle not the box itself). The stores leave the boxes on the shelf for a long time.
a month or two
Forever and Forever and Forever .
6-20 washes
Depends on how many times you wash your hair.
raw hair dye.
It depends on the dye you used: if it was temporary when you shampoo your hair the dye will wash out straight away. If it is semi permanent it was last 6-8 washes, if it is a quasi permanent you get 12-24 washes and if it is permanent it won't fade. So depending on how long your dye will last you can wash your hair when you like.
It doesn't last very long, about the same as temporary dye which is 1-2 washes. It depends on what type marker you use
As long as their are no chemicals (such as bleach) in your hair dye, then you can't dye your hair too much. A brand I know, that doesn't have any chemicals in the hair dye, is Manic Panic.
Yes, you can dye your hair after using Sun In a long time ago. It will not hurt your hair at all.
You should leave your hair for about 2 weeks before you dye it again. This will give your hair chance to settle and recover from the last dye.
about 2 weeks
If you are talking about hair Color stay in longer and it looks more natural to me , dye is when you put a certain kind of color in your hair that does really last long and it is also about the product you use to ....