Toastbrewt

Nah, they changed that. The beta entry in your game library is now deprecated. Just right click the normal Arma 2 Operation Arrowhead go to propterties -> beta tab and opt out of all betas.

"Bad Version. Server rejected connection" is always an issue with your arma 2 version. Try checking the server's name you wanted to join. They usually have their arma 2 version displayed there. If the version is >112555 and you are using steam try checking the game integrity or opt out of all arma 2 betas.