Matrix SCB Developer Cream with 9% 30 Volume Creme Developer

Hi, im wanting to dye my beard grey, like white/grey. What do i mix with this??

Can I apply this directly to my hair or do i need to mix it with bleach ?

I want to use so color 4n to cover my natural brown, some greys and some vibrant red I have in my hair. What is the best recommended developer?

It is this developer for hair colour dye?