Multiaccount Help

I've recently got a 5 month old account from my friend. He has logged on it before I got it (to change the passwords and email). How long should I wait before I'm able to play on it without flagging the account? Or am I able to play on it immediately?

You can play on it, but if you were banned for multi accounting you're propably ip banned aswell so I suggest you using a vpn like SoftEther and change uniqueId, uninstallid and hardware serial number. (Use osu! profiler and West Beginning)