how to reactivate a deactivated account

See -> How to deactivate your Apple ID account

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

👉 scroll to How to temporarily deactivate your Apple ID

Sign in with your Apple ID at privacy.apple.com on your Mac, PC, iPhone or iPad. Then scroll down to Data and Privacy, and select 'Manage your Data and Privacy'. On the following page, select 'Get started' under 'Deactivate your account'. If you don’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. 

BTW: 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.