How to add a recovery contact and enable Advanced Data Protection on iPhone?

The following is extracted from --> Set up an account recovery contact - Apple Support (IN)

"How to set up an account recovery contact

Find out how to set up an account recovery contact on your iPhone or iPad with iOS 15 or iPadOS 15 or later, or on your Mac with macOS Monterey or later.

On your iPhone or iPad

1. Go to Settings, then tap [your name].
2. Tap Sign-In & Security, then tap Recovery Contacts.
3. 
   
4. 
5. Tap Add Recovery Contact, then follow the onscreen steps to authenticate.
6. If you’re in a Family Sharing group, the members of the group will be recommended. Or you can tap Choose Someone Else to choose one of your contacts.
7. 
   
8. 
9. If you select a family member, they’ll be added automatically. If you select a contact, they'll need to accept the request. You’ll also send them a message to let them know that you’d like to add them as your recovery contact.
10. After they’ve accepted your request, you will see a message that they have been added as your account recovery contact. 

If your friend or family member declines or removes themselves as your recovery contact, you will see a notification and will need to select a new account recovery contact. "

On iPhone or iPad · Open the Settings app. · Tap your name, then tap iCloud. · Scroll down, tap Advanced Data Protection, then tap Turn on Advanced Data Protection ...

How to turn on Advanced Data Protection for iCloud

arlynnat wrote:

Does it mean that someone else has full access to my iPhone account?

No, not at all. They can only help you recover your Apple ID account credential.

"How to get a recovery code from your recovery contact

If you forget your Apple Account password or get locked out of your account, just follow the steps on your device to share the on-screen instructions with your recovery contact in person or over the phone. Your recovery contact will then share a 6-digit code that you enter on your device. Once your identity has been confirmed, you can reset your Apple Account password."

arlynnat wrote:

My phone started glitching and losing battery power quickly in the past month. What do I do?

This is nothing to do with Advanced Data Protection or adding a Recovery Contact.