It's a chemical, follow the instructions. If you want to leave a dye in overnight, try something natural-like henna.
no
It will gradually fade back to your natural hair color. Semi-permanent colors only deposit..they do not penetrate the hair they just coat the strand of hair.
Yes, but you can get a funky color if you do it wrong.
Do you mean pastel hair dye? It depends on if you use a permanent dye or a semi-permanent. Semi-permanent hair dyes will wash out and fade over time; permanent hair dyes will stay in the hair until you cut it or dye it another color.
yup
yes
Yes, demi permanent hair color can be applied over any type of color. It will refresh the original color very nicely.
yes you can will it kill your hair yes but you can
Yes. Over time it will permanently lighten your hair.
No you have to leave it for at least 3 weeks before you dye your hair. You can only use a temporary colour (that lasts one wash) until then but these they not over any gray coverage.
yes but if you want to go red for instance you need to build it up
apply all over