setup a security code but forgot the code how can i use my i phone

If you have forgotten the Passcode, You will need to restore the device using a computer. The process will erase the device. Later you can restore your data from a recent back-up. Instructions here…

If you forgot your iPhone passcode - Apple Support

If you have forgotten your Apple ID Password, see this link...

If you forgot your Apple ID password - Apple Support

"forgot the code have face id set on my phone but can"t log into phone"

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Troubleshooting Face ID:

Overview these links:

• About Face ID Advanced Technology - Apple Support

• If Face ID isn't Working on your iPhone or iPad Pro - Apple Support

• Learn which iPhone and iPad Models Support Face ID - Apple Support

• If an Alert Says Face ID has been Disabled on your iPhone or iPad Pro - Apple Support