restriction time passcode

If you forget your 4 digit Screen Time Passcode

4 Digit Passcode is for Screen Time Restrictions

4/6 Digit Passcode is for iPhone lock screen

Make sure to choose a passcode that's different from the passcode you use to unlock your device. If you can't remember a restrictions passcode that you set on a previous version of iOS, or you forgot your Screen Time passcode, you need to erase your device, then set it up as a new device to remove the passcode. Restoring your device from a backup won't remove your passcode.

https://support.apple.com/en-in/HT204396

Use Screen Time on your iPhone, iPad, or iPod touch - Apple Support

https://support.apple.com/en-in/HT208982

You may be being asked for a former Restrictions passcode, or a current Screen Time passcode.

Perhaps you're involved in Family Sharing and a family member created the passcode.

If you cannot remember the passcode, you must erase the iPhone and set it up as new.