I forgot my iCloud password

1.

It depends on what you did with your 'old Apple ID'. If you have deleted it, it is no longer valid, it simply no longer exists and it no longer works.

To understand about a deleted Apple ID, see the Apple articles below:

How to delete your Apple ID account

How to delete your Apple ID account – Apple Support (UK)

Understand and control the personal information that you store with Apple

Understand and control the personal information that you store with Apple - Apple Support

2.

If you've ever requested to deactivate your Apple ID, see

See -> How to deactivate your Apple ID account

How to deactivate your Apple ID account – Apple Support (UK)

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How to temporarily deactivate your Apple ID

Sign in with your Apple ID at privacy.apple.com on a Mac, PC, iPhone or iPad, and select "Request to deactivate your account". If you can’t see this option, it means that this feature is not available in your country or region. 

When you request to deactivate your account, you receive a unique alphanumeric access code. Make sure that you keep this access code in a safe place – you must have it to reactivate your account. 

After we verify that you are the account holder making the request, we deactivate your account.

Can I reactivate my account?

Yes. If you request account deactivation, you'll receive a unique alphanumeric access code. When you're ready to reactivate your Apple ID, contact Apple Support, provide your access code and we’ll help you reactivate your account. If you lose this code, we won't be able to help reactivate your account. 

3.

If you stil have / know that Apple ID, check your Apple ID via your email box, see this Apple article: If you forgot your Apple ID

If you forgot your Apple ID email address or phone number - Apple Support                  

OR see -> Having trouble signing in?

https://iforgot.apple.com/password/verify/appleid

Try this -> If you can't connect or sign in to iCloud

If you can't connect or sign in to iCloud - Apple Support

See this Apple article: If you forgot your Apple ID password

If you forgot your Apple ID password - Apple Support

Then see this Apple article: What to do after you change your Apple ID or password

What to do after you change your Apple ID or password - Apple Support