How to stream videos from icloud to iphone
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 &quot;listen&quot; 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