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Probably you are viewing Memories on the Photos App.

Go to the Photos app on your iPhone. · Tap Collections. · Swipe left under Memories to scroll through a selection of your memories, or tap Memories to view them.

View your memories in Photos on iPhone

If you feel an unauthorized person/app is remotely using, controlling or monitoring your device, then that is possible only if you have done one or more of the following Don'ts...

1. Don't hand over an iPhone to kids or to a stranger without Enabling Guided Access
2. Don't share Apple IDs
3. Don't Jailbreak
4. Don't share sensitive information pertaining to your device
5. Don't give in to Phishing
6. Don't plug in your device in Airports and Public places through third-party cables and trust the device. Beware of Juice Jacking. (Especially in India)
7. Don't leave your iPhone unlocked and unattended in public places like offices, schools, malls, etc.

If one of the above is true then quickly change the Apple ID Password and Return iPhone settings to their defaults.

1. Immediately change your Apple ID password
   1. Go to Settings → [your name] → Sign-In & Security → Change Password.
   2. This signs out anyone using your account.
2. Enable Two-Factor Authentication (if not already): Same menu → Two-Factor Authentication → Turn On.
3. Check for any unknown devices linked to your account:
   1. Settings → [your name] → Devices.:
   2. If you see anything you don’t recognize, tap it → Remove from Account.
4. Check for unknown profiles or device management:
   1. Settings → General → VPN & Device Management.
   2. If you see a profile you didn’t install, tap it → Remove Profile.
5. Check Accessibility & Screen Sharing settings
   1. Settings → Accessibility → Switch Control, Voice Control, or Remote Control — turn off anything you didn’t set up.
   2. Settings → General → AirPlay & Handoff → make sure AirPlay is set to Ask or Never Automatically.
6. Sign out of iCloud everywhere and reset
   1. Go to Settings → [your name] → Sign Out (you’ll need your password).
   2. Then back up your photos to iCloud or your computer.
   3. Go to Settings → General → Transfer or Reset iPhone → Erase All Content and Settings.:
   4. Set it up as a New iPhone (not from a backup), so nothing suspicious is restored.
7. Update iOS: Always keep the latest iOS version for security fixes.

If a person has ever had your passcode, they could’ve installed something quietly — so the full erase and setting up as new is the safest option. How to factory reset your iPhone, iPad, or iPod touch