How do i view Photo horizontally from vertical

I almost always take pictures in horizontal mode, since that's the way my computer monitor and my TV work. So when I rotate my phone from vertical to horizontal, I (usually) want the picture to stay put and fill the horizontal screen. But sometimes I rotate the phone to see a picture that's sideways, so I want the picture to rotate with the phone.

I change how rotating the phone works in the Control Center.

Access Control Center on your iPhone - Apple Support

You get to the Control Center by swiping down from the top right of the screen, and you get this:

(I copied the picture from the support article, above.)

The icon with the little phone and rotate circle locks and unlocks the rotation. Control Center makes it quick to get to when you need it.

Let us know if this does what you need...

Are other apps rotating properly, or is it just photos that are stuck?

Cool!