how can I update games with an outdated ios

On my Ipod Gen 4 I have a game called TSTO (The Simpsons Tapped Out). I have an og account with a lot of old stuff on the account that I would like to get back. Unfortunately my ipod has an outdated ios so I can't update the game to get my account back. It would be wonderful if anyone knew how to update my ios so I could get into the game. I dont have another apple device besides my brothers iPhone x (yes I have a Samsung but I'm gonna switch soon). He already has the game so idk if it will work or not. If anyone can figure this out I will be so happy! Thanks!