i forget icloud password

the activation lock is not really on the iphone it's a

theft protection measure on apples servers

it needs to be removed How to remove Activation Lock - Apple Support

if you don't know your appleID Recover Your Apple ID - Apple

if that does not help you then you need the assistance of apple

Additional Support - Activation Lock (apple.com) and or

Get Support (apple.com) , Genius Bar Reservation and Apple Support Options - Apple

iCloud uses Apple ID credentials.