Answer:
I'm as simple as a circle worthless as a leader; but when I follow a group their strength increases tenfold. By myself I'm practically nothing.
I'm white and used for cutting and grinding. When I'm damaged, humans usually remove or fill me. For most animals I am a useful tool. What am I?
You use me between your head and your toes the more I work the thinner I grow.
What has many keys but can't open a single lock?
An action done on mosquito bites
The answer I give is yes, but what I mean is no. What was the question?