file-sharingfiles.appicloudiphonesharing
My Documents and Desktop folders from my Mac have been backed up to iCloud. I would like to watch some videos from iCloud, via my iPhone without downloading. But when I open Files app from iPhone, it just downloads the media file to my phone. I know even though I streamed, I'll consume the same amount of data, but if I stream rather than downloading I'll save some time.
So, in summary, my question is:
How to stream a video file from Documents, from iCloud to iPhone?
Yes. I've done this many times.
The iCloud restore process deposits the sandboxed saved application data, but not the application package itself.
As a second step, you can sign into the store to re-download the apps (or connect to iTunes to transfer the apps) so that it matches the data, but I see no reason why you can't get at the data using whatever tool can read the filesystem such as a jailbreak or PhoneView.
It appears that you've added a video to an iCloud Shared Photo Stream. Since you are the one that added it to the stream, you can delete it.
Can I delete photos, videos and comments from a shared stream?
Yes. If you are the owner of a shared stream, you can delete any photos, videos or comments that you or your contributors have added.
Source: Apple KB article: iCloud Photo Sharing FAQ
To delete a video from a shared stream:
Go to Photos → Shared.
Select the stream that you added the video to, then select the video.
Tap the Trash 
icon to delete it.
To delete the entire shared stream:
Go to Photos → Shared.
Select the stream that you wish to delete.
Go to People → Delete Photo Stream.
With regard to your statement about using up iCloud storage…
Do Shared Photo Streams use my iCloud storage?
No. Photos uploaded to Shared Photo Streams do not count against your iCloud storage.
Source: Apple KB article: iCloud Photo Sharing FAQ
Best Answer
iCloud is a file synchronization service, not a streaming service. So, the short answer is - you cannot.
There's a big difference between opening a file and streaming a file.
When you open files, whether it be on your local device like your computer or your phone, across the network to/from a shared folder on a friends computer or from a file server or even across the Internet, it is copying the file to a local store before it opens it to play it.
When you stream a file, a service on the server (remote) will open the file and broadcast the contents of the file (audio/video) over the network. The (local) client will then "listen" for this network traffic, capture it, then play it.
iCloud doesn't do this; it's not AppleTV. Even Apple Music synchronizes your music files