iPhone question if you can help. [View all]

I am a simple user and text friends. I am able to delete texts when the conversation is over...except:
I am not able to delete the text from my daughter. No matter what I do, the delete options does not show. I have no idea what is causing this, any ideas about how to find a way to delete what is now a very long text?

Also, I was told by my other daughter that I had all kinds of apps within the phone.
She told me to go ho my home screen, double click button and swipe up,
OK, which is the home page, the one I see when I push the button to activate or the one that shows with all the icons?

Yes, I am an old timer who was given this phone with no instructions so I'm on my own.It is about 40 miles to an Apple store for help. so here I am. Any help would be appreciated. Thanks,
PR