Can I download porn so it’s in my iPhone without anyone finding out?

Hi was wondering if I could downloaded porn onto my iPhone onto one of those apps that hide photos/videos will my family’s shared computer with other iPhones on the same computer but different accounts be able to see that I’ve downloaded it and will it sync onto the computer and then onto there iPhones and are u even able to download porn onto ur iPhone without a computer and is there an app that u can view porn or like play for it? Would be great if u could help