See -> If you can't connect or sign in to iCloud
If you can't connect or sign in to iCloud - Apple Support
See also -> If your Apple ID is locked or disabled
If your Apple ID is locked or disabled - Apple Support (CA)
-> Get a verification code and sign in with two-factor authentication
Get a verification code and sign in with two-factor authentication - Apple Support
You can contact Apple support for help, -> Get Support (apple.com)
You have to show proof of ownership of your product, provide all documentation showing your purchase of the device.
If you do not have additional proof of ownership, contact the reseller. They may be able to provide the original purchase document.
Once Apple receive your proof of ownership, Apple will further review your request and provide an update.
FYI -> You are sign in here . . . with your Apple ID & Password (?).
Your Apple ID is the personal account you use with all Apple products and services. It includes the email address and password you use to sign in, as well as the contact, payment, and security details that you use with Apple.
You can’t merge multiple Apple ID accounts.