I want to change the home screen wallpaper. When I try to change the home screen wallpaper it chooses a past wallpaper for me and won't let me pick a different one, and when I try to pick a different one, it will let me but only on the lock screen. I'm not sure if this is because of the update.
Sometimes wacky things happen after we update. Try rebooting your device by pressing & holding the power & home buttons at the same time until the Apple logo appears.
What "update"?
What iOS version is on the phone?
Have you tried hard resetting the device by pressing the Home button and Power button at the same time and holding them until the you see the Apple logo?
Also, you might try adding a new wallpaper from the photos app. Highlight the wallpaper > Tap the share arrow in the lower left corner > Tap "use as wallpaper"> follow prompts.