Thread moved to the Account Help forum, where assistance is best provided on this sort of issue.
If you've lost all forms of multi-factor authentication for the account (presuming this is a Jagex Account as you mentioned backup codes), you may be out of luck. Part of the security improvements provided by Jagex Accounts is that 2FA cannot be bypassed if you no longer have the details for it, without those backup codes there simply isn't a way back in.
15-Jan-2024 13:00:51