To turn off restrictions on an iPhone, follow these steps depending on your iOS version: For iOS 12 or later:

1. Open the Settings app on the iPhone.
2. Scroll down and tap on "Screen Time" (an hourglass icon).
3. Tap on "Content & Privacy Restrictions."
4. If the toggle switch next to "Content & Privacy Restrictions" is on, tap it to turn it off.
5. You will be prompted to enter your Screen Time passcode. Enter it to confirm.
6. This will disable all content and privacy restrictions on the device.

For iOS 11 or earlier:

1. Open the Settings app.
2. Tap on "Restrictions."
3. Select "Turn Off Restrictions."
4. Enter the Restrictions passcode when prompted.

If you don't remember the Screen Time or Restrictions passcode, you can reset it using your Apple ID password by going to Settings > Screen Time > Change Screen Time Passcode > Forgot Passcode?, then authenticating with your Apple ID to create a new passcode and disable restrictions. Disabling restrictions removes app, content, and privacy limitations imposed by Screen Time, allowing full access to all iPhone features and content.