Yes.
Settings > General > Reset > Erase all content and settings erases everything.
Yes.
Settings > General > Reset > Erase all content and settings erases everything.
Yes.
Settings > General > Reset > Erase all content and settings erases everything.
If you mean using the “erase all content and settings” feature in the settings app, then yes, that will delet ALL your data. As will restoring the device as new in iTunes.
will erasing content clear my messages