Deleting photos on the phone - does it affect them on iCloud?
Whilst it does depend on where you delete the photo, it also depends on what you mean when you say 'iCloud'…

Here are three scenarios involving deleting photos on your iPhone, and the result of doing so:


Delete from Camera Roll

Deleting a photo from your camera roll only removes it from your camera roll. The photo is left intact on Photo Stream if it has already been uploaded. A photo not yet uploaded to Photo Stream will not be uploaded to Photo Stream after it has been deleted, even if partially uploaded.

However, deleting a photo from your camera roll, then using iCloud Backup, will delete the photo from your iCloud Backup. This means that the photo will not be restored if you restore a backup from iCloud. (If a photo does not exist on your iCloud Backup, and is deleted before it is uploaded, it will not be part of the next iCloud Backup).
Delete from Photo Stream

Deleting a photo from Photo Stream will only remove it from Photo Stream. It does not affect the photos in the camera roll, or even Shared Photo Streams - they keep a copy of the photo separately.

Since it does not affect the camera roll, it will not affect any iCloud Backups, both previous iCloud backups and future backups.
Delete from Shared Photo Stream

Deleting a photo from a Shared Photo Stream will only remove it from that Shared Photo Stream. It will not affect other Shared Photo Streams, the main Photo Stream, or your camera roll.

Since it does not affect the camera roll, it will not affect any iCloud Backups, both previous iCloud backups and future backups.