I want to delete a video from my camera roll. Will it still exist in some kind of backup? This video was not uploaded to the cloud or the photo stream.
Videos deleted from the camera roll are permanently gone from your phone. Even if you had your phone backed up to iCloud, your storage profile would update, after the video was deleted, so that the video would be removed from the cloud as well.
You will have to manually backup the video onto your computer, or email it to yourself before deleting it if you want it saved.