Hair and Nails

Hair dye

Q: I have heard it's permissible to use black dye, but I have a doubt. Nowadays we can't say what all the ingredients in the packets are. Is all type of dyes allowed?I have heard that our wudhu and bathing won't be correct since its a kind of paint. Often the hair colouring damages our hair. Knowing about such (scientific) damages, does Islam say "no" to use such types of dye.

Uneven haircut

Q: I am a boy. When I go to the barber shop, I ask him to cut my hair short on my sides and the back of my head. But I ask him to keep the front hairs relatively bigger than those at the back. Is it permissible or must all the hairs be cut equal from all sides?