press home and the power switch until the iphone begins to shut down. Once it does. Release the power switch and continue pressing "home". That will take u to the DFU mode ( euta taarrr computer ma or k ma connect bhako jasto dekhaune mode) once that comes. Connect ur iphone to the computer that has itunes. Detect garcha iphone lai....click on the detected iphone and on ur right hand side u will see option like restore, update etc(khai k ) tara once u get to that screen u will see "restore" option. Press that..and wait until it completely restores the iphone. The passkey problem will be gone.