Is watching a pornographic film on a phone that may have the name "Abdullah" displayed on it considered disbelief, and is it permissible to say "Alhamdulillah" to a friend online who posts pictures of immodestly dressed women?

Watching pornographic films is a heinous sin, and a Muslim must stay away from them in obedience to the words of Allah Almighty: (Tell the believing men to lower their gaze and guard their private parts). Whoever watches them is not considered an apostate, but is a sinner.