How to reset iPhone passcode?

See the information in the Related Article above your name in your post. You can also check this if you have the latest iOS. How to remove your iPhone, iPad, or iPod touch passcode without a computer - Apple Support

You can't. put your phone in recovery to reset it

If you can't update or restore your iPhone or iPod touch - Apple Support

You can make an itunes backup just in case if you remember it again.