I want to install ios 12.4.4

1) 12.4.4 never released for the 6s or all other devices capable of running iOS 13. Last version of iOS 12 for those devices was 12.4.1.

2) You can not restore or downgrade to a previous version of iOS.

No that is not possible. iOS 12.4.4 is for iPhone 5S, iPhone 6/6 Plus, iPad Air, iPad Mini 2, iPad Mini 3 and iPod Touch (6th generation) only