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You got the Chinese version before it got trade locked. As long as its activated on your account you're fine. They could potentially add a "onlyallowrunincountries" tag and then you'd be fucked, but its very unlikely they do that.

Region doesn't matter in terms of who you'll be able to play with. Online is governed by Rockstar Social Club anyway. Kind of like Ubisoft is with uPlay. So yes, you'll be able to play with your friends fine :P

CN = China, and im not sure how u were able to activate it, since you cant buy gta 5 as gifts from china anymore "Notice: Grand Theft Auto V is not available for purchase as a gift in China.", or maybe the gift was bought before it got locked.
i dont know what to tell u, once i got a free steam key of Hitman Absolution Sniper Challenge from a chinese site (had no restriction when i activated it), and after i bought a new pc that was capable of running newer games, tried to install it and it said something like "you are not in the right region to play this game"

EDIT: the online dealer logged into my account and somehow bought the game for $29, am I fucked?

Isn't this a form of VPN kinda? You might be fucked.

"EDIT: the online dealer logged into my account and somehow bought the game for $29, am I fucked?"

im about 99% sure that you wont be able to run GTA 5 as long as you're not in China and you'll have a hard time explaining that to steam support