Photos stored inside the app can be managed on the photos tab. Go to the photos tab, open the album, tap the “Select” button, tap photos to select them, then tap the delete button. Photos cannot be recovered after they are deleted.
When a photo is exported a copy of it is placed in a location outside of Context Camera, such as the photo library on your device. These copies cannot be deleted from inside Context Camera. You will need to use a different app to delete them, like the Photos app to delete photo library photos or the Files app to delete iCloud photos.