Does the game give away free UC? Like in events or special quests/missions? Or the only way to earn UC is by buying it?

You get free UC when you accomplish enough RP missions, part of your awards are UC. Anyone who says you don't is wrong and I don't understand why anyone would say that.

The only way to get "free" UC is to get the Royal Pass as you'll get 350UC by the end of this season from the rewards
I guess the other way is to download a survey app and answer a hell of a lot of questions until you have money to buy some....that's kinda free
Sorry bro...currently it's not possible but however try to spend BP in soldier's crate and dismantle extra items to earn silver frags which can be used to get cool stuff

Don’t be so sure about that. Last time people used UC trick a few months ago didn’t get anything. It was surely much less than now (people created tons of gmail accounts and got 120UC for each gmail Acc they created) but no one got any punishment. Honestly, after seeing people getting free UC, I don’t wanna spend a cent in this game.