The giveaway is over now but if you still want to know: République was offered on Twitch Prime in January 2019. If you didn't claim it to your Twitch account then, you can't get it on Twitch unless they decide to offer it again in the future. I don't know if the Steam version is the same as what was offered on Twitch Prime, but I've found that when they offer the games on Twitch, they usually come with all the DLC and extra content. Hope this helps :)