How do I know when to use back or close button (or both) on mobile

I want to know when and why should I use the X or back button on top of the page. And additionally, related to that, how should I judge the transitions, when should a page just slide from the right

Use the side, Home, and other buttons on your iPhone - Apple Support

Build Social Media Like App Twitter Instagram From Scratch

Cancel button vs back navigation - Design Thinking - UX Mastery Community

How to close apps on your Android phone

android - When to use close vs Up navigation/Back icon in screens - Stack Overflow

How Safety Check on iPhone works to keep you safe - Apple Support

How To Bring Back The Android Back Button [Back Button Missing]

Build Social Media Like App Twitter Instagram From Scratch

Touch and hold the back and Recent button at the same time to cancel Screen Pinning Android Phone

What is the main difference between the cancel button and the back button in UX mobile design? - Quora

7 rules for mobile UI button design, by Justinmind

Buttons Not Working on Your Android Phone? 5 Fixes and Workarounds

Unsend and edit messages on iPhone - Apple Support

Designing A Better Back Button UX