am i able to print off a picture on printer paper and us that as a stencil or something like that?

I have done this! So, you print off the picture. Get a black ballpoint pen, some gel type deodorant (I used my husband's), and a blank sheet of printer paper. Trace the printed picture with the ballpoint pen onto the blank paper. Then cut it out in the general shape of the design. Then cover the area on your skin you want the tattoo with the deodorant completely. Place the traced paper ink side down to the deodorant covered skin. Press and hold for about 30 to 45 seconds. And voila! You now have a nice outline to trace with the freehand ink!

What if you mess up, can you wash it off right away or will it show in 24 hours?

If you wash it off right away, it may still show up faintly, but it won't last. I drew a quick and simple design, smudged it almost immediately, washed it off and redid it, and the first version was faintly visible under the darker, final version. The faint version disappeared after a couple days though, whereas the final version (which sat for the entire hour) lasted almost exactly two weeks like it was supposed to.

Can it be used on eyelids...as eyeliner?

Actually technically yes u can... U maybe shouldn't but I have and I have friends who have.... If ur rlly good at eyeliner get a old eyeliner marker with a pointed tip and draw it on in little bits at a time starting with it being gray and washed out and then build on as the first layer is semi dry.

No. I bought it for my daughter, she LOVED it. It's ink, so it goes on your skin, it's not applied with needles. You just draw like you would with an ink pen.