Can you get information if you forgot your password of an old phone through your Apple ID?
Can you figure out your old password on a device signed into your Apple ID?
iPhone 6s Plus, iOS 12
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If you have forgotten the passcode, you will need to restore the device to remove it and then you can restore your latest backup for content. See the instructions here, If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support or watch this video for assistance.