I want to advertise Brave on the most popular social network in Russia vk.com .Can i do this? If so, which referral link should I use
You can use whatever referral link(s) you want. 
VK campaigns are okay, but we still request that you not use ‘brave’ in any of your keywords. Doing so will result in your account being suspended.
Did I understand correctly that I can’t use “brave” as a keyword in my ad campaign? Sorry for the question, I just don’t know English well
Yes, “brave” and any variant of it is not allowed as ad keywords