1.
See this Apple article: Downgrade or cancel your iCloud+ plan
Downgrade or cancel your iCloud+ plan - Apple Support (PH)
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Before you downgrade or cancel your iCloud+ plan, first download or remove content that exceeds your new storage amount. To make sure that you don't lose any information, learn how to copy what you store in iCloud.
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2.
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)
-> Once your account has been deleted, Apple can't reopen or reactivate your account or restore your data.
Understand and control the personal information that you store with Apple
Understand and control the personal information that you store with Apple - Apple Support
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3.
Note:
Never post your Apple ID credentials (such as Apple ID, billing address, phone number, etc.) on a public forum, that is asking for trouble.
Have asked the host to remove it.