Sheikh alsalam alaikum, sheikh there is a game i repented from playing to contains shirk etc.. but there is an additional mode that came out that has nothing into it but it unlocks only if u completed the main story (which ive done before repenting) . Is playing this mode nullify my repentence?

Ustadh AbdulAziz al-Haqqan

No, what breaks a repentance is returning to the sin itself. But, I advise you never to return this game no matter what. Once you give something up for the sake of Allah don't go back to it.