How do I set a password to prevent turning off iPhone 16 Pro?

This (Passcode to turn off) feature is not available.

Switched Off? Still Traceable: Even if the iPhone is switched off, it is findable; see the picture below.

iPhone is findable even when powered off. (iOS 15 and above)

Did you enable Find My network? See the pic below

If yes, read below how it may get located.

The Find My network is an encrypted, anonymous network of hundreds of millions of Apple devices that can help you locate your device.

From the above, I infer that when another device comes in close proximity to your powered-off device the GPS/Bluetooth from both devices will form a network and your device's location info will be displayed to you on your device only. As long as both devices are/have...

• Find My Network is enabled
• iPhone 11, 12, 13, 14, and above
• With iOS 15 and above versions

Set up Find My on your iPhone, iPad, iPod touch, or Mac

If you are worried about losing your iPhone and the safety of your personal data, it’s essential to take proactive steps to secure your device and your information. Here’s a comprehensive guide to keeping your iPhone and its data safe:

1. Use a Strong Apple ID Password: Your Apple ID is the key to your iCloud, App Store, and other Apple services. Make sure your password is long, unique, and difficult to guess. Avoid using easily accessible information like birthdays or common words.
2. Enable Two-Factor Authentication (2FA) – This adds an extra layer of protection, requiring a verification code when signing into your Apple ID on a new device.
3. Set an Alphanumeric Passcode: Instead of the standard 4- or 6-digit passcode, opt for an alphanumeric passcode that combines letters, numbers, and symbols for enhanced security.
4. Enable “Find My iPhone”: This feature helps you locate your device if it’s lost or stolen. You can also remotely lock or erase your device to protect your data.
5. Turn on Stolen Device Protection: This feature adds extra security by requiring your Face ID, Touch ID, or passcode for certain actions when your device is away from familiar locations.
6. Set Up a Recovery Contact: If you ever forget your Apple ID password or get locked out of your account, a recovery contact can help you regain access.
7. Enable Advanced Data Protection: This provides end-to-end encryption for more of your iCloud data, including photos, notes, and backups, making them accessible only on your trusted devices.
8. Take Automatic iCloud Backups Daily: Ensure that your device backs up automatically to iCloud every day when connected to Wi-Fi and charging. This keeps your data safe and up to date.
9. Use Guided Access Before Handing Over Your iPhone: If you’re giving your iPhone to a child or a stranger temporarily, enable Guided Access. This restricts the device to a single app and prevents access to other parts of your phone.
10. Never Share Your Apple ID: Sharing your Apple ID compromises your privacy and security, leading to potential data mix-ups and unauthorized access.
11. Avoid Jailbreaking Your Device: Jailbreaking removes Apple’s built-in security measures, making your device vulnerable to malware, hacking, and unauthorized access.
12. Protect Sensitive Information: Never share your device’s serial number, IMEI, or other sensitive data with untrusted sources.
13. Be Wary of Phishing Attempts: Don’t click on suspicious links or provide your Apple ID credentials in response to unsolicited messages or emails.
14. Avoid Using Public Charging Stations: Public USB ports, especially in airports and other high-traffic areas, can be compromised by a technique known as “juice jacking,” where malicious code is installed on your device through the charging cable. Always use your own charger and plug directly into a power outlet.
15. Keep Your Device Locked and Supervised in Public: Never leave your iPhone unlocked and unattended in public places like offices, schools, malls, or restaurants. A moment of distraction could lead to theft or misuse.

By following these best practices, you significantly reduce the risk of losing your device or having your personal data compromised. Stay vigilant and prioritize your iPhone’s security wherever you go.