This app was mentioned in 13 comments, with an average of 3.23 upvotes
I use this app. No affiliation.
You select the photos you want to share, then share using the app. It basically locks the viewer in to just view those photos until the pin is entered.
But screen pinning just pins the app. So if you pin the gallery you can just browse and flip between other photos.
You need Focus which lets you lock a single iamge or a selection of images, which can be swiped between but the user can't view any other images from the gallery, or view other apps. You can pin focus and have the user just look at the app with the selected images you choose (or you an pin protect Focus to prevent the user unpinning the app and browsing around).
May I recommend Focus for android? You share the photos with the app and you can only see those until you input a PIN.
https://play.google.com/store/apps/details?id=com.risesoftware.focus.free&hl=en
Or use an app designed to prevent people from swiping, such as this one
For this use case, you can alternatively use an app like Focus, you just share the photo to the app, and it isolates it.
I use Focus - Photo Sharing in conjunction with screen pinning. Works for me.
Since you mention wanting to show pics to other people, try this app:
https://play.google.com/store/apps/details?id=com.risesoftware.focus.free&hl=en
Or focus. It might not be as fun though.
This app is perfect for this.
https://play.google.com/store/apps/details?id=com.risesoftware.focus.free
Allows you to set some photos and a pin. Escaping requires the pin. No more accidental dicks.
Bound to be something similar on iOS.