Can’t modify Apple ID

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.

Keep in mind: You can’t merge multiple Apple ID accounts.

What happens when you use the same Apple ID & Password that you use to sign in here?

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

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

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

See this Apple article: 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

For more support and assistance see -> Contact Apple for help with Apple ID account security

Contact Apple for help with Apple ID account security - Apple Support

What happens when you try to change the password? Error message(s)?

If you know your Apple ID password.

 Apple ID Password Change.   -  

ASC YouTube for How to reset your Apple ID password

 What to do after you change your Apple ID or password - Apple Support  -   I suggest doing this before you change your Apple ID or password.

If you forgot the Apple ID (iCloud) password, enter the Apple (iCloud) ID, and click Forgot Password. See if you can get a Rescue or Notification email option if necessary. Link to contact Apple Support at the end of the 2nd article.

Apple ID - Manage

Apple ID – Forgot Password  *      

If you have 2 Factor Authentication enabled, if you can't recover the password using the steps above, you will need to use Account Recovery. The Recovery Process is an automated process and the length of time it takes can vary a lot. Apple ID Support can only answer your questions. They can't intervene in or speed up the process. The article below has some suggestions to shorten the time the process takes.

Apple ID - Recover your Apple ID with two-factor authentication account recovery.   *