This hair color contains developer or, we use it directly without any additions?

You can put it in your hair straight or add conditioner to lighten the color pigment. But I wouldn't recommend using any developer with it.

does crystal clear works as virgin snow by Manic panic (as a toner for blonde to white hair )??

Hi!:') No, it works more like a glaze. Remember when John Frieda had clear glaze (was awesome... )- it's like that. Hope that helps!

can conditioner be added if the color is too bright? Looking for a pastel pink.

You CAN ABSOLUTELY mix with conditioner, but there are pastel shades available. I mix cotton candy and petal pink for a beautiful pastel pink and no conditioner added. You could lavender or light blue.

Apparently dye comes off if I shampoo with Head and Shoulders. Is that true?

Head and Shoulders is known to strip even permenent hair color done at professional salons. My colorist discourages using Head and Shoulders whenever you can avoid it (it should never be your regular shampoo because it even damages non-colored hair). I found that using Pureology shampoo, I keep vibrant Adore color for months with regaular washing. A small amount of Pureology goes a long way.