You're trying way too many things in quick succession, which is confusing this issue a lot - Jagex Accounts are not like RuneScape accounts, so the things you're used to doing don't work the same.
Your issue here is that you aren't receiving verification emails. However, you know that your email is correct, because it is the email that you use to login with to get to the 'pick your verification method' screen, and you have received verification emails there before. If you change your email, your Jagex Account login email changes too, so we know this is the right email.
To me, this says there is an email delivery issue between Jagex and your email provider (looks like an Outlook email from your screenshots). There is likely not much you can do except wait at that point for one end or the other to resolve it, however your account is still secure since you need an email code to log in, and no one but you has access to your email.
You won't have backup codes unless you have set up verifying via an authenticator app on your Jagex account. Those would be provided to you as a downloaded text file named "Jagex - Backup Codes.txt" and will contain 10 single use codes you can use to log in with. If you did set up an authenticator app for your Jagex Account, that should be an option on the verification screen for you, and you can use that to get into your account.
Jagex accounts
cannot be recovered via the old RuneScape account recovery system
, hence your last screenshot - that is coming from the old system.
Unlinking an account from a Jagex account and restoring the old credentials isn't possible either, those are permanently disabled once an account is imported to a Jagex account. Similarly, an account cannot 'unlink' itself from a Jagex account as you noted in page 2 post 1.
09-Apr-2023 17:15:53