My Qs were more specific
It is easier to answer specific question, when I know whch options you are having on your computers. I.e. I wondered if you would be able to use Shared PhotoStreams instead of My Photo Stream, but that would require MacOS X 10.9. at least, see: iCloud: Using and troubleshooting Shared Photo Streams
( pls see above): 1/ I was assuming that via iCloud only " my Photostream" is distributed onto all aktivated iOs- devices;
The Photostream "My Photo Stream" uses a buffer in iCloud: Each device will upload the most recent (last month) photos saved to the Camera Roll, if Photo Stream is enabled and any photo you share to the stream. The buffer in iCloud will only keep the photos for a month - it is meant as a streaming buffer and not as a storage. And the stream you are seeing on your devices is fed from this buffer. Depending on when you activate Photo Stream on the devices they will show different selections of photos - it depends on what is currently in iCloud. With IOS 7.0.4 you could also stream to Shared Streams, and they will keep all photos in iCloud, only you would need to upgrade.
- having said so: does iCloud then back up my Camera Roll ( Photos) in toto ?
Your Photostream is generated automatically from all photos saved to your camera roll, so if you keep all photos in your camera roll and save any new photos from the Photo Stream to your camera roll, they will all be backed up, inclding any videos in your camera roll. This list describes in detail, what automatically will be backed up in iCloud over Wi-Fi:
See: iCloud: Backup and restore overview
2/ the 2nd Q posed was: Is there a mechanism to save/ backup on the Album level ( I guessed it can be done via iTunes), but also through iCloud (??)
That is exactly, why I asked for your system versions: if you could create Shared Streams, you could use 100 separate streams just like albums, and all would be stored in iCloud.
But there is no way to structure "My Photo Stream".
But the iCloud backup of your devices will include all application data, so albums you define in the Photos app will also be included, only not the photos synced to your device using iTunes, unless you save them to the camera roll.
- Does one then HAVE TO make b/u via iTunes for EACH iOs device ( and of course the whole Library file
You can make your iCloud backup using Wi-Fi (iCloud: Backup and restore overview), but you will have more control over it, when you create the backup using iTunes. And syncing using USB is faster than Wi-Fi.
4/ Does one have to save (B/U) as well via iTunes into the iPhoto library,
as also via iCloud (?)
It is recommended: the iCloud backup of your IOS devices will enable you to restore your devices directly from iCloud, but a separate backup in iTunes will make it possible to restore a new replacement device from the backup, if your iPad, iPhone will be stolen, lost, or defective. And you can access the iTunes backup even when the network is down, or there is a problem with your iCloud account.
iPhoto library: When you automatically import the photoStream into your iPhoto library on your Mac, any backup of your iPhoto library will be a backup of your Photo Stream photos as well. I'd create the albums in iPhoto on your Mac.
Some Links:
iCloud: My Photo Stream troubleshooting
iCloud: Photo Stream FAQ
Regards
Léonie
A remark about Photostream : its deletion logic for pics, once 1000 is reached is intransparent
This is explaine d by the fact that "my Photo Stream" is not meant to be a storage, just a transient buffer. You have one month time to grab your photos from the stream, and then they will be removed, consider it to be a stream of photos that you are viewing from a narrow window. You are supposed to download the photos to your camera roll or to an event on your mac, as soon as you are seein it in the stream. After a month it will be gone.