Salon Care 20 Volume Creme Developer, 32oz

Are these bottles suppose to have a seal on them after you remove the cap? Just wondering, since the 16oz I got does not have one.

I was looking for something that would be thicker than normal peroxides. Is this a thick consistency?

Liquid or powder dye for this?

I have dark hair if i use the 20 would it go up to blonde ? Or do i have to use 30 or even 40 but kinda scare